Was wondering myself so just tested it out on an auction I was watching. Once you are the high bidder, you can continue to bid 1 penny at a time to "increase" you max bid. Because you are already the high bidder, you do not need to meet the minimum bid increment like a different bidder would.
That said, he could have bid $42.49 and 1 penny up each time to be at $43 total. This is pretty crappy IMO, but I really hope someone else wins the auction
Well, here we go. We have other bidders now so we can see his bidding pattern. It is quite random, but in smaller increments ranging from about 10 cents to $1.50. He is still winning, but the shirt has already gone higher than expected. He bid 51 times in about 10 minutes, his second to last bid was 70.01, then he bid one more time about 20 minutes later, not sure why.