2 + 2 = 4.000000001?

[Kevin Willis]

I was wondering is any body else has noticed strange answers to 
simple arithmetic problems with using the calculator in OS 10.2.8. 
When I add a string of whole numbers together, I end up with a rather 
long decimal in the answer.  I have tried it with the basic and 
advanced calculator and with and without the tape.  Is it safe to 
trust it with important figures?

Thanks

Kevin