If you have a rounded value like ROUND(VALUE,2) in the detail section and when you try to do a total in SSRS you might find yourself having a Rounding problem. As you can see below the sum of the total is off by a penny.

The original expression for the total was like this. However, instead of summing the rounded values SSRS was actually summing the values and try to round it which is causing a problem.

The only way I was able to fix the problem was treating the value as a string and do a rounding using Format() function like FORMAT(VALUE, “#,0.00”) then since the value becomes a text convert it back to decimal using CDEC(). Finally, you could run your SUM() as usual.

As you can see this fixed the problem and the report shows correct amount 90 cents.