You'll notice that each item in the auction has a timer, ticking away the minutes and seconds until the item closes. If there are any bids placed during the last five minutes, the time resets for an additional five minutes. This will occur indefinitely until there are no bids.
This is very much one of those love/hate features of Auction Ninja. One the one hand, you have time to place a competing bid (and consider whether you want to place a bid). On the other hand, it can feel like a never-ending loop if there are competing bids.
Most people are familiar with eBay's platform, which does not have a timer reset - once the time runs out, it's over. While this is certainly a simple and straight-forward method, it does leave open the possibility of unfair advantages by those that use bid sniping programs. A soft close, like Auction Ninja uses, is similar to a live auction format.