you can do this in t-sql using Format function.

Declare @tbl table ( id int, assignment decimal(11,8))

insert into @tbl

select 1, 10.00 union all

select 1, 8.55 union all

select 1, 0.55

select id, assignment, format(assignment,'###.##') AS assignment_format

from @tbl

As per BOL the return data type will be in nvachar. Koen Verbeeck is rightly said that

hope it helps