Sorry, there was no comment about change in using of parameter.

I tried:

DECLARE

@enumerator DECIMAL(38, 12)

,@denominator DECIMAL(38, 12)

SELECT

@enumerator = 5

,@denominator = 111.111

SELECT

dbo.fn_BRound2(@enumerator/@denominator, 2)

,Round(@enumerator/@denominator,2)

Result:

.0400.050000

Still need to try harder.