In general, I tip a flat $5 for food deliveries (pizza, Uber Eats, etc.) and $10 for grocery deliveries since they have to carry more stuff to my door. I may do more than that for special circumstances, but I find tipping the same amount every time makes it easier for me to ensure it’s fair across the board and I haven’t shorted anyone. That said, I’m only ever ordering for myself - I’d probably adjust amounts if the orders were for multiple people and routinely had a lot of items.