Bartering for Beers

Perhaps this is just one of those "guy things," but does anyone else trade off money for beers and drinks all the time?  Or do my friends and I need to get some professional help?

We were just emailing back and forth about our trip to Philly and I made the majority of the reservations with my credit card, and while telling the guys what they owed me, I rounded it off to a lower, even, number and said "you can just buy me a beer this weekend."   I think its a male ritual or something, or do women do it too??