You'll need to create an account, then you can go in and add up to 5 gift cards at a time (I don't remember the exact verbiage used on the site. I know there is a "check balance" in the same list. "Manage my cards" maybe?)... You'll have to transfer the balance of each card onto your one primary card, then delete the 4 empty ones, then add 4 more, and repeat.
Found it! Thanks!