I am getting incorrect answers in adding and subtraction

[Basher]

I am using Excell in Microsoft Office 2007 and am getting incorrect answers
to adding and subtraction it is mostly just a penny out

 

[Otto Moehrbach]

Look at the source of the numbers that are being used in the calculation of
the final number. While you see, say, 6.03 in a cell because the cell is
formatted to 2 decimal places, Excel may see 6.034. The final calculation
is made with 6.034 regardless of how you format that cell. This can easily
built up to a noticeable apparent error. HTH Otto

 

[Niek Otten]

It is all explained here:

http://www.mcgimpsey.com/excel/pennyoff.html