In two different spreadsheets I calculate the same figures with a slightly
different approach. One being a summary sheet of all certificates and other
one being a cash flow. Because of the rounding and different calculations i
get slight differences up to 3 cents. This is accepted. But for some reason
now the differences are up to 17.50 and 35 dollars. On the same sheet i do
the same exercise but now by doing smaller steps and get different answers!?

What is causing this?! What should I look for? please help