The whole point of sniping is to show no interest until the last second--to minimize the chance that folks who don't bid their maximum will respond at the last minute.
I recommend you decide what your max is and bid it at the last few seconds, regardless of whether or not there is a reserve. Stick with one price and you will either win it or be outbid by someone who was willing to pay more than you were. Whether or not there is a reserve is inconsequential when you snipe.