Numeric Values Functions - round
Applies to: 
SQL Server
Returns the number not having a fractional part that is closest to the argument. If there is more than one number like that, the one that is closest to positive infinity is returned. For example:
If the argument is 2.5, round() returns 3.
If the argument is 2.4999, round() returns 2.
If the argument is -2.5, round() returns -2.
If the argument is an empty sequence, round() returns the empty sequence.
Syntax
fn:round ( $arg as numeric?) as numeric?
Arguments
$arg
Number to which the function is applied.
Remarks
If the type of $arg is one of the three numeric base types, xs:float, xs:double, or xs:decimal, the return type is same as the $arg type. If the type of $arg is a type that is derived from one of the numeric types, the return type is the base numeric type.
If input to the fn:floor, fn:ceiling, or fn:round functions is xdt:untypedAtomic, untyped data, it is implicitly cast to xs:double.
Any other type generates a static error.
Examples
This topic provides XQuery examples against XML instances stored in various xml type columns in the AdventureWorks database.
You can use the working sample in the ceiling function (XQuery) for the round() XQuery function. All you have to do is replace the ceiling() function in the query with the round() function.
Implementation Limitations
These are the limitations:
The round() function maps integer values to xs:decimal.
The round() function of xs:double and xs:float values between -0.5e0 and -0e0 are mapped to 0e0 instead of -0e0.