Does bid sniper post my 'highest bid' to win the auction or a bid slightly higher than the next in line? Ie if I would like to bid on a car which is currently at 3k and I enter 6k into bid sniper will the bid entered by bid sniper be 6k or an amount $1 higher than the competiton?

Just found the answer in faq.

I'm glad you found the answer quickly.

Just for others to see:
The sniper will place the exact bid you specified. If nobody bids higher, you will win at the lowest possible price just enough to outbid the previous bidder by one increment only.
It's a good thing to put your absolute maximum when sniping -- most of the time you'll pay less.