Sometimes he seems really tight, but I don't think he is. He just like things "right".
E.g. we have some really big drinking friends. When we're out with them he sometimes doesn't buy a round. He does buy them but not every time, I think in his head he's evening things up for all the times he's spent more than he drank iyswim. Recently he's started staying out of rounds altogether if he's not drinking, which is better.
When we're out together we split everything, and I mean everything. He knows exactly who paid for which coffee, but it works both ways, he knows and will speak up when it's his turn, every time.
This weekend we visited my sister. I was going anyway and he tagged along. We had a lovely weekend, ate out three times, which I paid for (we often do this and split later). When we got home he asked what he owed me, without being nudged. I told him what I'd spent and he said "plus petrol". I said dont worry, I was going anyway, it was my trip. He's sent me what he owes plus petrol money anyway.
He doesn't ever "treat" me and doesn't want me to treat him, which all feels a bit odd, but I think it probably is OK, no red flags?