Add automatic 2% to all purchases

Hello,
I am trying to add an automatic 2% discount to all purchases via the shopping cart. This is in addition to the regular Group Discounts that I have on the cart,
Anyone knows how to do this? any ideas?

Thanks,

Amit

I found a way to do this by duplicating the Quantity Discount contrib and just changing the names in the contrib files to something else so there will be no conflict (I am currently using the Quantity Discount for something else).
My only problem is that the discount is on the original price and I want it to be on the reduced price. For example, if the quantity discount for the whole amount is 10%, and the total amount before the discount was $100, I want it to discount additional 2% from the $90 and not from the pre-discounted $100 - makes sense?

Thanks,

Amit