This is answered in the Help tab on AuctionSnipers site. Look at question #2
http://www.auctionsniper.com/?p=newfaqWhat if two or more people snipe the same item at the same time? Although the probability of this happening is very small, we have developed our software to give bidders an equal chance of winning in all possible cases.
For example: If two bidders are sniping on the same item with the same max bid, and both choose to snipe with just 5 seconds left -- our bidding system will send eBay both bids at the same time.
The rest is up to eBay. The winner will be the bid that eBay received first. We do not have control over which of eBay's servers we send to, and therefore, we cannot pre-determine who will win.