I dunno, they just do! We all had Westgate Ark t-shirts on and there were labels on the buckets - we just had a bucket sat at the end of each till.
I didnt even have to ask people - I just did it. We did one at Tescos that had a LOT more tills and got about £850, but needed a lot more help. At that one I did get sick of saying 'do you want a hand with your packing?' A lot more people there brought there own bags and were a lot more picky about their packing.
I personally hate anyone else packing my bags, but at B&M it was mostly tins, sweets, pop and booze!
I might order some pairs of cat ears for the next lot of fundraising we do!