I like what you did with sales exceptions and purchase exceptions. Didn’t think of that but it is a problem across most localizations.
However, this is too much. It then rolls into other totals.
I’m strongly considering to drop the idea of having dual-purpose tax codes for both sales and purchases and simply replace it with single-purpose tax codes. Yes - we end up with more tax codes but report transformations should be easier to author and understand as a result.