Here's what it sounds like to me:
5 items that are (for example) 60%, 40%, 85%, 15% and 25% close to the ARP. For example, if there is a $20 item and it is the 60% close price, then the price displayed is $12. There is a 6th item that has a displayed price equal to the ARP. The task is to pick the item(s) that total 100% without going over.
Winning combinations are
1. 60% + 40%
2. 85% + 15%
3. 60% + 15% + 25%
4. 100%
(These 4 combinations correspond to the 4 wvoutlaw2002 posted.)
If they get 100% exactly, they get both the car and $5,000. If they get, 40% and 25% and wish to stop, then they get 65% of $5,000, which is $3250--and no car. If they go over 100%, they win nothing.
(Am I understanding the rules correctly, wvoutlaw2002?)
If I'm right, it sounds too similar to Hit Me. In Hit Me, we had a displayed price * number from 1-10 = ARP; here we have displayed price * % = ARP. If most of the population can't do addition or multiplication well enough to make Add 'Em Up and Hit Me a successful game, then I doubt this will be any more successful--if this was an actual pricing game.