Casting the float to a VARCHAR value is what causes the rounding you are seeing:

select

a.MyFloat,

ToVarchar = convert(varchar(30),a.MyFloat),

ToLtrimRtrim =ltrim(rtrim(a.MyFloat))

from

( Select MyFloat = convert(float,10041.25E00) ) a

Results:

MyFloat ToVarchar ToLtrimRtrim

---------------------- ------------------------------ -----------------------

10041.25 10041.3 10041.3