Offset: Round offset value for the sake of floating errors

IE10+ may return not exactly the offset.top value set in an offset callback
if parent has fractional top offset itself. Checking for being close to the
desired result fixes the test error.

Fixes jquerygh-2147

test/unit/dimensions.js

@@ -453,15 +453,18 @@ testIframe( "dimensions/documentLarge", "window vs. large document", function( j
 });
 
 test( "allow modification of coordinates argument (gh-1848)", 1, function() {
-	var element = jQuery( "<div/>" ).appendTo( "#qunit-fixture" );
+	var offsetTop,
+		element = jQuery( "<div/>" ).appendTo( "#qunit-fixture" );
 
 	element.offset(function( index, coords ) {
 		coords.top = 100;
 
 		return coords;
 	});
 
-	equal( element.offset().top, 100, "coordinates are modified" );
+	offsetTop = element.offset().top;
+	ok( Math.abs(offsetTop - 100) < 0.02,
+		"coordinates are modified (got offset.top: " +  offsetTop + ")");
 });
 
 })();