same product item with different prices based on quantity

We want to run a special.We have a total of 7, all featuring product xxx. different quantity of product xxx triggers a different discount.We can get it to work perfectly for one combo. But if we add a product from another combo (e.g. 2x xxx, 1x yyy and 1x ttt) then it adds both discounts incorrectly. OR we can get it to only apply one discount but we can’t have it apply multiple discounts if multiple combos are added