P.S 8.2.0: discount from first price tax included and than add tax another time

[monak1983]

Hi to all, I'm a B2B ecommerce and first I think is needed a little introduction to understand my request.
My business is selling B2B clothing with high discounts prercentage from retail price, on this business is common use add an high discount to retail price (tax icluded) but sell adding tax to discounted price:

- 1st price (retail price) 100 (tax included)
- 80% discount = 20
- add tax (vat 22% in Italy) -> 20+22%=24.4

I'm on PS 8.2.0 and only solution I have found is this:
- configure PS showing prices without tax
- update all prices adding another time tax via sql -> 100 (tax included) becomes 122 (tax included twice)
- add discout 80%
- cart will shows 20 + 22% = 24.4

On this way I will have expected bheavior but all first prices are modified and is not a good solution.
Any suggestions or better ideas?
Thanks a lot.
monak1983

Edited January 3 by monak1983 (see edit history)