General :: Conditional Formatting Percentage Result

I have a subform based on a query. In that query, I have calculated values for price+tax and another price+discount+tax. Now I have a conditional formatting that if the gross total is not equal to amount due, the amount due box will turn red. However even if they are equal visually, it still turns red. Ex. The gross total is 336.00 and the amount due is 336.00 also, so it should NOT turn red, but it does. When I click on the amount due control, the value turns into 335.999999195337. How do I tell access not to make 336.00 into 335.999999195337.