I've recently been able to afford things rather easily and I also live with flatmates (who are also coworkers). We all make the same amount and share a lot of stuff.
Whenever I feel like it, I just buy them things like a coffee when I'm having one at work or I pay for the week's groceries. They also do this at about the same frequency.
However, one of them still seriously asks me:
"Hey I owe you amount right?"
I'm not sure how to respond to that. I usually laugh and tell them to shut up, because I'm not expecting them to deposit cash my way. But, in retrospect, it would be a lie to say I'm not expecting camaraderie in some way.
What would be a proper response to have others forget about keeping tabs without sounding pedantic or dismissive?