To stop the misplacement of items in the wrong sack, I drive my wife absolutly insane by segregating the items as I place them on the conveyor. It's been a source of lots of teasing from her. But hey, I put the refrigerated items on the belt first...then all other dry food items...then canned goods...next, non-food items (toiletries, laundry goods, etc) ...and finally all crushables like bread, eggs, chips and cookies. She teases me all the time about it....but I still do it. When I get home, everything is segregated and easy to put in its place.
As far as tipping....I haven't had a kid offer to help me out with my groceries in years...lazy little bastards. If they did...sure i'd tip. (policy or no) So the buggy (that's what they call them here in the south...not a "cart") goes wherever it won't roll accross the parking lot. Screw them guys...that's job security for them. The only exception to this is when I stop at a store while I'm in my tractor/trailer rig. Usually when that's the case, I'm parked nearly as far from the store as is possible...so I do at least give them a shove in the direction of the corral.
Ern