Ah yes forgot about Publix - and yeah more than once I have been asked by Publix employees if I needed help pushing the cart - they seemed to be happy to do it too!
Publix is the best. My wife's family used to work for them and the benefits were great.
Free college tuition for one. Defined retirement. Very decent health care (better than a well known Southern multinational you've heard about corporate care)
It's all gone now, I believe, now that the family list control of it (but I thought the employees owned half of it :S ?)
When I worked there as a bagger many years ago, it was expected. If the customer said no, we were to insist. Even then, we'd get looks from management if we let too many buggies leave the store without us. Also, we'd get in serious trouble if we accepted a tip.