Thank you for the additional information.
So Myanmar’s 5% commercial tax, while not legally considered a value added tax, operates as an offsetting tax. Therefore, it can be set up in Manager just like other in-built tax codes. I will invite @lubos into this discussion so he sees the need to add it to the program.
You also appear to possibly be subject to the special goods tax. However, there are so many different possible tax rates, it would be difficult to include them all. So it is probably best to handle those as custom tax rates. Note that because Commercial Tax is imposed in addition to the special goods tax, you will need to calculate compound rates as you define custom taxes.