I grew up in England and always disliked the custom of "rounds" for several reasons. One is that you often end up drinking more than you wanted. Let's say you are in a group of four. Your preference is to have two drinks, but the round has to finish, so you either refuse the third and fourth drink while paying for four (or not paying if you didn't buy the first or second round) or you drink four anyway to be sociable.
One solution we used was to have a "pot" where everyone put enough money in for a couple of drinks. The drinks were paid for from the pot, and when it was gone everyone had the right to either put more money in and continue drinking or stop paying and drinking. It works if everyone is having the same (costing) drinks, like beers, as was often the case and also if the group stays the same.
Over here in the USA, the normal thing is to have a "tab" where all the drinks are paid for at the end of the evening, and the cost can be divided up then.
