I wouldn't raise the offer either like you are thinking. If they won't give you a counter they will wait for your next offer and then counter. They will squeeze more money out of you.
If you really want the car then decide on your absolute highest price you are willing to pay then either:
1. Offer that price and tell them this is your best offer and there is no room for negotiation. If they don't accept it then just move on. Be prepared to walk using this method. If they come back a day later with a counter just tell them you are already looking at other vehicles and the only way you will consider theirs is if they meet your price. There are plenty of cars out there.
2. Offer lower then your best offer and see if you get a counter and play the stupid negotiation game. Just be prepared to cut it off at some point. They will try and squeeze every cent out of you.