While Auction Sniper sends eBay your maximum bid, this does not mean that you will always pay this amount. Often times you will pay less.
For example: An item is currently $20.00, and you bid a maximum of $50.00. Instead of the auction suddenly jumping to $50.00, it will only raise to $21.00 -- which is the minimum bid above $20.00.
So, to answer your question more specifically -- Auction Sniper will not bid less if it is possible for you to win for that amount, but instead, eBay will take care of that.
Adam R.
Auction Sniper Support