Tax part works, calculator not so good

As a tax app it works well. Adding and breaking out sales tax is excellent. Allowing multiple tax rates makes It useful for marking up and down pricing as well.
The calculator part is inconsistent when adding long strings of numbers.
The placement and labeling of the backspace key results in frequent errors. If the backspace key were relocated next to the clear key it would be better.
I find I need to use a different calculator to sum my invoices.

RSwec about Tax Me Pro