Seth, it sounds like the autobid feature eBay uses. Say the current bid price is $100 and I put my max bid in at $125. It will automatically bid for me up to that price in whatever the minimum bid is. If it is a $5 minimum the current bid will be $105.
Now if another bidder comes in and puts a max bid of $120, eBay will bid in those $5 incrments back and forth and the bid will now be $125, my max, and I would be the high bidder. Because other bidders can't see my max bid, and don't usually want ot drive the price up, most bidders wait til near the end of hte auction ot bid. You should read eBay bidding policies and descriptions. It will help you to understand what is happening.
Jack