I had no problems doing 2 transaction of 3x $100. All the $200 were already sold out. The cashier was curious and simply just asked what the deal was and told him.
Just an FYI, extra cards are stored inside of the gift card rack, at least at the OfficeMax I went too. Think a manger might have to open it but they let me take a look inside for $200s but their were none.