Cash Bar Sales and Concessions

We are attempting to place Cash Bar Sales within Theatre Manager. Since our Cash Sales include Sales Tax, we back out the sales tax and then input the amount within a Resource Description so that the tax is then added on, in order to reach the same total amount that we sold the product for.

Unfortunately, we sometimes get a cent error due to this process.

Has any one come up with this issue and if so, has rounding been your best option or have you found a work around that suffices.