E-commerce tax calculation when coupons are applied

Basically, when applying a coupon, the tax is calculated based on the initial amount, not the discounted amount, which is wrong. Also, when entering the coupon code at checkout (public cart), it automatically sends the user to the next screen (address or whatever), which does not give the user a chance to see the discount be applied and see the amount they have to pay. Maybe add a button "Apply Coupon", update the info on that page, but don't skip to the next step. Secondly, that page needs to have a better breakdown of how the coupons impact the items in the cart (since more than one coupon is allowed to be added)You should have it as item 1 original price ..... xxx Coupon XYZ 5% OFF item 1 subtotal ....... xxx - 5% Similar breakdown for item 2,3,4 etc. Subtotal........................ $$$ Tax................... $$ (applied on subtotal above) Total ............................... subtotal + tax. Thanks,Sebastian