Discount not on VAT?

Hi,
I'm using HikaShop Essential. When I create a coupon discount of 50% and sell 2 products of € 5,=. The price without discount is € 10,=. But when I use the couponcode the price is not € 5,= because the discount is not calculated over the tax.

Example:
In the Netherlands we have 19% VAT.
Price incl. VAT: € 5,= (€ 4,20 excl. VAT)
Buying two of these products with 50% discount, must result in"
€ 4,20
€ 4,20
€ 8,40
€ 1,60 VAT
€ 10,00 total
€ 5,00 -/- (50 % discount)
€ 5,00 total price of this order.

But when I use this couponcode the endprice is now € 5,80! (that is € 4,20 + € 1,60)

So in this exemple the discount is calculated over the price excl. VAT, while the VAT is still calculated over the price without the discount. That is not how it should be.
----
I also like to display al the prices in the cart incl. VAT.
I've read this:
www.hikashop.com/en/forum/4-how-to/38735...uded-vat-prices.html
And this:
www.hikashop.com/en/forum/4-how-to/28960...-with-tax.html#28986

I added $this->params->set('price_with_tax',1);
after the first <?php tag of the file "step" of the view "checkout" that you can edit via the menu Display->Views
but nothing changes.

Can you please help me with these issues.

Hi Nicolas,

1. The option "apply discount" was the right solution for the discount and VAT issue. Thanks a lot!

2. For the prices incl. VAT in the cart, I made changes in the file "cart" for the front end. But maybe I have to try it again. I let you know if it works or not....