Estimated Total and Order Total are not the same

So, when I go to checkout on Marketpress, I get an estimated amount, tax, and estimated total. On this page, everything is correct. However, when I finalize the order, on the last page, it gives me Order Amount (this is right), tax, and then Order Total (this is WRONG). The Order Total doesn't add in the tax, as it did on the previous page. Does anyone know why this is happening?