Tips for pizza delivery?

I have a Domino's literally one mile from my apartment. It is literally on the same street as me.

I placed a delivery order for two large pizzas. What do you think the tip should be?

And to anyone who has done pizza delivery, why do companies charge such a high delivery fee? $5 in Domino's case, and it doesn't even go to the driver? So insane.

Oh and to anyone who wants to say "why didn't you just pick it up?", stfu. I don't want to leave my apt today. Life is like that sometimes.