Have Coupon applied to Total?

Can someone tell me if its possible to change the way Opencart calculates the discount so it bases it on the total of the cart rather than the sub-total.

I am using an extenstion for some "buy 2 for £10" deals, but what seems to be happening is the coupon completly ignores this.

Example: 1 product is £5.99 or buy 2 for £10. Sub-total shows £11.98 but then with the promotion applies takes off the £1.98 to make the total £10. However if a 10% discount code is then applied the coupon gives £1.20 discount instead of £1 and then total to pay becomes £8.80 when it should be £9.

I have tried changing the order totals and no matter where I put the coupon code or the special offer the result is the same.

My store is: http://www.eliquidworld.co.uk you replicate this problem by adding 2 of this product http://www.eliquidworld.co.uk/E-Liquid/Amaretto-20ml to the cart then adding discount code POTV

Any ideas on how to fix this?

Painfull slow, along with a painfull Javascript View-Disturber, personally, I would not waste my time, as shopper, trying to 'push' my browser trough such..., without registering first.
Try to play Customer, and think like one, beeing able to choose from a huge variety of places.
just thinking...
Good Luck
Ernie

Sorry, was your reply meant for this post?

Are you saying my site is very slow loading? as this doesn't appear to be the case when I run tests on it such as Pagespeed and GTmetrix.

Anyway we are in the process of upgrading to 2.x now so maybe we will figure the problem out on the new version.