diff --git a/rdflib/plugins/sparql/operators.py b/rdflib/plugins/sparql/operators.py
index 7e9e4d1ca..908b1d5c5 100644
--- a/rdflib/plugins/sparql/operators.py
+++ b/rdflib/plugins/sparql/operators.py
@@ -16,7 +16,7 @@
 import re
 import uuid
 import warnings
-from decimal import ROUND_HALF_UP, Decimal, InvalidOperation
+from decimal import ROUND_HALF_DOWN, ROUND_HALF_UP, Decimal, InvalidOperation
 from functools import reduce
 from typing import Any, Callable, Dict, NoReturn, Optional, Tuple, Union, overload
 from urllib.parse import quote
@@ -205,7 +205,7 @@ def Builtin_ROUND(expr: Expr, ctx) -> Literal:
     # this is an ugly work-around
     l_ = expr.arg
     v = numeric(l_)
-    v = int(Decimal(v).quantize(1, ROUND_HALF_UP))
+    v = int(Decimal(v).quantize(1, ROUND_HALF_UP if v > 0 else ROUND_HALF_DOWN))
     return Literal(v, datatype=l_.datatype)
 
 
@@ -381,7 +381,7 @@ def Builtin_CONTAINS(expr: Expr, ctx) -> Literal:
 
 
 def Builtin_ENCODE_FOR_URI(expr: Expr, ctx) -> Literal:
-    return Literal(quote(string(expr.arg).encode("utf-8")))
+    return Literal(quote(string(expr.arg).encode("utf-8"), safe=""))
 
 
 def Builtin_SUBSTR(expr: Expr, ctx) -> Literal:
@@ -471,7 +471,10 @@ def Builtin_SECONDS(e: Expr, ctx) -> Literal:
     http://www.w3.org/TR/sparql11-query/#func-seconds
     """
     d = datetime(e.arg)
-    return Literal(d.second, datatype=XSD.decimal)
+    result_value = Decimal(d.second)
+    if d.microsecond:
+        result_value += Decimal(d.microsecond) / Decimal(1000000)
+    return Literal(result_value, datatype=XSD.decimal)
 
 
 def Builtin_TIMEZONE(e: Expr, ctx) -> Literal:
diff --git a/test/test_sparql/test_functions.py b/test/test_sparql/test_functions.py
new file mode 100644
index 000000000..fb544142c
--- /dev/null
+++ b/test/test_sparql/test_functions.py
@@ -0,0 +1,189 @@
+import logging
+from decimal import Decimal
+
+import pytest
+
+from rdflib.graph import Graph
+from rdflib.namespace import XSD, Namespace
+from rdflib.plugins.sparql.operators import _lang_range_check
+from rdflib.term import BNode, Identifier, Literal, URIRef
+
+EG = Namespace("https://example.com/")
+
+
+@pytest.mark.parametrize(
+    ["expression", "expected_result"],
+    [
+        (r"isIRI('eg:IRI')", Literal(False)),
+        (r"isIRI(eg:IRI)", Literal(True)),
+        (r"isURI('eg:IRI')", Literal(False)),
+        (r"isURI(eg:IRI)", Literal(True)),
+        (r"isBLANK(eg:IRI)", Literal(False)),
+        (r"isBLANK(BNODE())", Literal(True)),
+        (r"isLITERAL(eg:IRI)", Literal(False)),
+        (r"isLITERAL('eg:IRI')", Literal(True)),
+        (r"isNumeric(eg:IRI)", Literal(False)),
+        (r"isNumeric(1)", Literal(True)),
+        (r"STR(eg:IRI)", Literal("https://example.com/IRI")),
+        (r"STR(1)", Literal("1")),
+        (r'LANG("Robert"@en)', Literal("en")),
+        (r'LANG("Robert")', Literal("")),
+        (r'DATATYPE("Robert")', XSD.string),
+        (r'DATATYPE("42"^^xsd:integer)', XSD.integer),
+        (r'IRI("http://example/")', URIRef("http://example/")),
+        (r'BNODE("example")', BNode),
+        (r'STRDT("123", xsd:integer)', Literal("123", datatype=XSD.integer)),
+        (r'STRLANG("cats and dogs", "en")', Literal("cats and dogs", lang="en")),
+        (r"UUID()", URIRef),
+        (r"STRUUID()", Literal),
+        (r'STRLEN("chat")', Literal(4)),
+        (r'SUBSTR("foobar", 4)', Literal("bar")),
+        (r'UCASE("foo")', Literal("FOO")),
+        (r'LCASE("BAR")', Literal("bar")),
+        (r'strStarts("foobar", "foo")', Literal(True)),
+        (r'strStarts("foobar", "bar")', Literal(False)),
+        (r'strEnds("foobar", "bar")', Literal(True)),
+        (r'strEnds("foobar", "foo")', Literal(False)),
+        (r'contains("foobar", "bar")', Literal(True)),
+        (r'contains("foobar", "barfoo")', Literal(False)),
+        (r'strbefore("abc","b")', Literal("a")),
+        (r'strbefore("abc","xyz")', Literal("")),
+        (r'strafter("abc","b")', Literal("c")),
+        (r'strafter("abc","xyz")', Literal("")),
+        (r"ENCODE_FOR_URI('this/is/a/test')", Literal("this%2Fis%2Fa%2Ftest")),
+        (r"ENCODE_FOR_URI('this is a test')", Literal("this%20is%20a%20test")),
+        (
+            r"ENCODE_FOR_URI('AAA~~0123456789~~---~~___~~...~~ZZZ')",
+            Literal("AAA~~0123456789~~---~~___~~...~~ZZZ"),
+        ),
+        (r'CONCAT("foo", "bar")', Literal("foobar")),
+        (r'langMatches(lang("That Seventies Show"@en), "en")', Literal(True)),
+        (
+            r'langMatches(lang("Cette Série des Années Soixante-dix"@fr), "en")',
+            Literal(False),
+        ),
+        (
+            r'langMatches(lang("Cette Série des Années Septante"@fr-BE), "en")',
+            Literal(False),
+        ),
+        (r'langMatches(lang("Il Buono, il Bruto, il Cattivo"), "en")', Literal(False)),
+        (r'langMatches(lang("That Seventies Show"@en), "FR")', Literal(False)),
+        (
+            r'langMatches(lang("Cette Série des Années Soixante-dix"@fr), "FR")',
+            Literal(True),
+        ),
+        (
+            r'langMatches(lang("Cette Série des Années Septante"@fr-BE), "FR")',
+            Literal(True),
+        ),
+        (r'langMatches(lang("Il Buono, il Bruto, il Cattivo"), "FR")', Literal(False)),
+        (r'langMatches(lang("That Seventies Show"@en), "*")', Literal(True)),
+        (
+            r'langMatches(lang("Cette Série des Années Soixante-dix"@fr), "*")',
+            Literal(True),
+        ),
+        (
+            r'langMatches(lang("Cette Série des Années Septante"@fr-BE), "*")',
+            Literal(True),
+        ),
+        (r'langMatches(lang("Il Buono, il Bruto, il Cattivo"), "*")', Literal(False)),
+        (r'langMatches(lang("abc"@en-gb), "en-GB")', Literal(True)),
+        (r'regex("Alice", "^ali", "i")', Literal(True)),
+        (r'regex("Bob", "^ali", "i")', Literal(False)),
+        (r'replace("abcd", "b", "Z")', Literal("aZcd")),
+        (r"abs(-1.5)", Literal("1.5", datatype=XSD.decimal)),
+        (r"round(2.4999)", Literal("2", datatype=XSD.decimal)),
+        (r"round(2.5)", Literal("3", datatype=XSD.decimal)),
+        (r"round(-2.5)", Literal("-2", datatype=XSD.decimal)),
+        (r"round(0.1)", Literal("0", datatype=XSD.decimal)),
+        (r"round(-0.1)", Literal("0", datatype=XSD.decimal)),
+        (r"RAND()", Literal),
+        (r"now()", Literal),
+        (r'month("2011-01-10T14:45:13.815-05:00"^^xsd:dateTime)', Literal(1)),
+        (r'day("2011-01-10T14:45:13.815-05:00"^^xsd:dateTime)', Literal(10)),
+        (r'hours("2011-01-10T14:45:13.815-05:00"^^xsd:dateTime)', Literal(14)),
+        (r'minutes("2011-01-10T14:45:13.815-05:00"^^xsd:dateTime)', Literal(45)),
+        (
+            r'seconds("2011-01-10T14:45:13.815-05:00"^^xsd:dateTime)',
+            Literal(Decimal("13.815")),
+        ),
+        (
+            r'timezone("2011-01-10T14:45:13.815-05:00"^^xsd:dateTime)',
+            Literal("-PT5H", datatype=XSD.dayTimeDuration),
+        ),
+        (
+            r'timezone("2011-01-10T14:45:13.815Z"^^xsd:dateTime)',
+            Literal("PT0S", datatype=XSD.dayTimeDuration),
+        ),
+        (
+            r'tz("2011-01-10T14:45:13.815-05:00"^^xsd:dateTime)	',
+            Literal("-05:00"),
+        ),
+        (
+            r'tz("2011-01-10T14:45:13.815Z"^^xsd:dateTime)	',
+            Literal("Z"),
+        ),
+        (
+            r'tz("2011-01-10T14:45:13.815"^^xsd:dateTime)	',
+            Literal(""),
+        ),
+        (r'MD5("abc")', Literal("900150983cd24fb0d6963f7d28e17f72")),
+        (r'SHA1("abc")', Literal("a9993e364706816aba3e25717850c26c9cd0d89d")),
+        (
+            r'SHA256("abc")',
+            Literal("ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad"),
+        ),
+        (
+            r'SHA384("abc")',
+            Literal(
+                "cb00753f45a35e8bb5a03d699ac65007272c32ab0eded1631a8b605a43ff5bed8086072ba1e7cc2358baeca134c825a7"
+            ),
+        ),
+        (
+            r'SHA512("abc")',
+            Literal(
+                "ddaf35a193617abacc417349ae20413112e6fa4e89a97ea20a9eeee64b55d39a2192992a274fc1a836ba3c23a3feebbd454d4423643ce80e2a9ac94fa54ca49f"
+            ),
+        ),
+    ],
+)
+def test_function(expression: str, expected_result: Identifier) -> None:
+    graph = Graph()
+    query_string = """
+    PREFIX eg: <https://example.com/>
+    PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
+    CONSTRUCT { eg:subject eg:predicate ?o }
+    WHERE {
+        BIND(???EXPRESSION_PLACEHOLDER??? AS ?o)
+    }
+    """.replace(
+        "???EXPRESSION_PLACEHOLDER???", expression
+    )
+    result = graph.query(query_string)
+    assert result.type == "CONSTRUCT"
+    assert isinstance(result.graph, Graph)
+    logging.debug("result = %s", list(result.graph.triples((None, None, None))))
+    actual_result = result.graph.value(EG.subject, EG.predicate, any=False)
+    if isinstance(expected_result, type):
+        assert isinstance(actual_result, expected_result)
+    else:
+        assert expected_result == actual_result
+
+
+@pytest.mark.parametrize(
+    ["literal", "range", "expected_result"],
+    [
+        (Literal("en"), Literal("en"), True),
+        (Literal("en"), Literal("EN"), True),
+        (Literal("EN"), Literal("en"), True),
+        (Literal("EN"), Literal("EN"), True),
+        (Literal("en"), Literal("en-US"), False),
+        (Literal("en-US"), Literal("en-US"), True),
+        (Literal("en-gb"), Literal("en-GB"), True),
+    ],
+)
+def test_lang_range_check(
+    literal: Literal, range: Literal, expected_result: bool
+) -> None:
+    actual_result = _lang_range_check(range, literal)
+    assert expected_result == actual_result