What is the largest gift that a US postal carrier can accept before they have to share it with everyone?

We're having a lot of packages delivered here soon, and our carrier always has such a great attitude. I want to get a gift card or some other gift, but I know they have limits on how much they can accept.|||Are all the packages being delivered at the same time? Or are they going to be delivered at different times? If they come at different times, just give him a smaller tip each time he comes. OR you could do the stalker thing, find out where he lives, and mail it directly to his house.|||I think that a regular thankyou card would suffice.|||I always thought they were not aloud to accept gifts - so a thank you card is what I give mine