SQL - Round a dollar value and update it in SQL

If I do that I get trailing zeros on the end.

For example, the value will be 45.0000  or 49.9500.

I need it to be 45.00 or 49.95

The Money datatype has 4 decimal places, so you will always see the two trailing zeros if you keep that datatype.  If you want the column to only have 2 decimal places, you need to change the datatype to something like DECIMAL(16,2).  Before doing that, you need to execute an update statement to round all the values to two decimal places as suggested above.

Changing the datatype and saving will automatically round the values, but no reason to take a chance, run an UPDATE statement first.

I'm not sure if you are looking to store data this way or just return data in this format. If you are looking to return data in this format, then you could use a convert() on select:
  SELECT CONVERT(decimal(16,2),TotalAmount) FROM table1

If updating:
  UPDATE table1
  SET TotalAmount = ROUND(TotalAmount,2)

When you read the data, you can also use cast

select Cast( round(TotalAmount,2) as decimal(16,2) ) as "TotalAmount"
from yourtable

The update statement is still correct, though.

After doing the update, you can:

select Cast(TotalAmount as decimal(16,2) ) as "TotalAmount"
from yourtable

in mysql there exist a truncate() function

mysql> SELECT TRUNCATE(-1.999,1);
        -> -1.9

i dnt know if such function exist in MS SQL

Arthur is correct. Not storing 4 digits to right of decimal to lead to greater problems.