I have a spread sheet for accounting but have a little problem in that the totals at the bottom of 3 columns do not add up to the total of the columns

They are out by a penny which is driving my mother ( & hence me ) insane . I think it has to do with the vat in that each entry is worked to 2 decimal places ( & rounded accordingly ) but I think the spread sheat is adding them all up to the zillionth decimal place & then rounding the total .How can I stop this & get it to just add the figures that are on display ?
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Colin
I trust my rebreather completely ,
I just don't trust the user
onwards & downwards