Trim decimal places from Varchar field

The ROUND function would work.
ROUND(<value>, 2, 1)

Error converting data type varchar to float.

Another option would be to use CHARINDEX to find the position of the period, add 2 to that value and then use LEFT:

LEFT(<value>, CHARINDEX('.', <value>) + 2)

As you have posted this in javascript, I assume you want the javascript to pre-format for you and the code for that is:

var twoPlacedFloat = parseFloat(yourString).toFixed(2);

Cd&

Based on the error you posted, I'm guessing you have non-numeric data (maybe empty strings or NULLs) in that field as well. You can use the ISNUMERIC function to filter out records that does not contain numbers in your field.