Can anyone who is an expert on Excell, please help me.

I need advice on adding up on Excell. The normal ADD function adds
everything, including, third, fourth and fifth hidden decimal places
etc, even though you are only viewing two decimal places. In
accounts, when cross checking, the total column adds up differently to
the across total, because it has added all the decimal places, but if
you add the actual figures shown in the column (two decimal places),
the total is different.

I know, somewhere there is a way I can get excell to CALCULATE to only
two decimal places and not just VIEW two decimal places, but I cannot
remember how to do it. Can anyone help.