Tiered Discounts applied to multiple lines of products

Would it be possible to have the tiered discounts working across more than one cart line? For example, it does 3% off for any product if at least three have been added, and 5% if at least five. If I add three of product A and five of product B, I would like to have the 3% discount applied to all of A, and 5% on B. However, it can only currently apply it to one type of product at a time. Thank you!