Round(x) Function

I saw there is a round() function that return the closest int from the numeric variable.
But there is no round(x) function that would return the numeric value with x decimal.

For example:

```
select round(192.4525, 2) -> 192.46
select round(2.3246, 2) -> 2.32 
```

Some doc here:
http://www.postgresql.org/docs/9.1/static/functions-math.html
