I put a few text books on ebay. They sold for $0.99 plus $4 shipping. These books are worth around like $100 each. I knew they wouldn't go for as much as they would have at the begining of a semester, but I need the money. How can I get out of this without being banned from ebay?
You might not be able to. If you wanted more than 99 cents for them, then why did you start the bidding so low? When you placed those items on eBay for bids, you made a legal commitment to sell them at whatever the highest bid was at the end of the auction. You don't have any legitimate reason to back out.

Your only option is to e-mail the buyer and explain that you're unable to sell the books to them and ask if they'll agree to mutually cancel the deal. Don't be surprised if they refuse to cancel, though. Why should they? You've promised to sell them a book they want at a very good price!