Discount calculation wrong

[ant1d0t]

Adding a discount coupon with negative amount without tax

coupon value = -10€
general value tax = 19%
tax not set

Adding such a coupon in t for easy discounts.
Without tax set not working/calculating correctly

1. User orders some items
   

2. User selects discount item e.g. -10€ without tax
   

Now the amount is taken off of the subtotal and total and Tax stays based on the inital amount. ^^

3. User selects discount item e.g. -10€ with tax The amount is subtracted from total amount anbd calculated correctly

gets popup modal warning
3. User deletes and it's lost forever

Expected result

without tax:

subtract from sub total and calculate tax for total

Current result

see above

scrennshots attached under relevant steps