I have several values that have been set to show only 2 decimal places,
but the actual value has more. When I sum the two cells I get the wrong
result.

For example

A1 = 23.34656 displayed as 23.35
A2 = 1.1072 displayed as 1.11

When the two displayed values are added the answer is 24.46 but if you
enter the formula A1+A2 the result is 24.45

How do I stop Excel doing this?