I'm trying to setup a rule that gives a free product every 5 buyed. This work if I add 5 products to the cart --> grand total is correctly reduced
But if I add 10 or more products the total amount of cat is reduced only by the price of 1 product.
I tried doing this myself and found it just wouldn't work - I could get close but there was always something not quite right, e.g. Buy 5 get 1 free, buy 6 and suddenly you get 2 free and so on.
In the end I found an extension to do it. The one that worked for me was Buy X Get The Cheapest Free by Zero1, but I imagine there are a few to choose from. Search Magento Connect or even just search in Google.