An alternative would be to have a "five-minute rule" where once the deadline kicks in, there is a period of five minutes in which if no other bids are received, the lot is considered sold. Each time an additional bid is received, the deadline is extended another five minutes until there is a five minute period in which no additional bids are received.

This is fair to the bidder and to the seller as anyone would be able to top the competitor's bid without having to resort to your $100 example.