I use Splitwise for this and it has been the perfect system for me and my roommate the past 6 months. Small things don't always get added in (like sharing some

I use Splitwise for this and it has been the perfect system for me and my roommate the past 6 months. Small things don't always get added in (like sharing some beers here and there), but most stuff does, and most importantly all of the communal items needed for the apartment. Who ever ends up owing at the end of the month just uses Venmo on there and it automatically zeroes everything out.