Well. I don't know if this applies. But with my boyfriend. We take turns paying for food - or we try split, depends on who has the more convenient coins to pay a near-half amount. But this is only when we share like big portions of food.
OTHERWISE. We pay for our own food. But I mean, sometimes we don't have enough money on ourselves and we cover each other. This is mainly because we are a bunch of high schoolers with no casual work - so no continuous flow of income.
Secretly, I like it when he pays for me sometimes.