Feature request from maderlock, posted on GitHub Jul 21, 2016
I would suggest there is a similar option to display discount incl/excl of VAT. The latter would add back the discount_tax_compensation amount so that the totals add up.
See example for why this currently is rather unintuitive:
Comment from maderlock, posted on GitHub Jul 21, 2016
I should note that the same issue exists in pdf. Looking at the discount values in module-sales/Block/Adminhtml/Totals.php, the correct value would be $this->getSource()->getDiscountAmount() + $this->getSource()->getDiscountTaxCompensationAmount() and similar for base. However, if I do this I end up with a 1p error in the order, though not the invoice! I thought the rounding since 1.8.1 sorted this?
I'd classify this as a bug.
Yes, I thought this was a bug, which is why I raised it on github. It was then moved here as it was classified as not a bug(!)