Do your Target orders contain only gift cards? Or do they also include an item that qualifies for cash back? Ebates generally excludes cash back for gift cards, but you can trick it to credit you for your entire purchase -- including the value of the gift cards -- if you add a qualifying item in with the order.
Here is the list of exclusions: Cash Back is not available on grocery, household commodities and essentials, baby care items (diapers, wipes, food, and toiletries), pet supplies, video games and consoles, music, books, contract mobile phones, prepaid and gift cards, Target Pharmacy and OTC, Target Photo, Target Optical, Target Café, SweetJOJO, and orders deemed by Target to be for resell.
We typically include a small, inexpensive item with our order, such as office and school supplies or beauty and personal care supplies. Check the category the add-on item is listed under to be sure it's not one of the exclusions, and even then it may still be cross-listed under an excluded category. YMMV.