Minimum 5 dollars, even if you're a few blocks away.
Your tip +$2.50 cents (what doordash pays their drivers) should add up to around 2 dollars per mile. If you live far away from restaurants that could potentially deliver doordash, add more because the driver has to drive back as well, which is a factor that drivers think about.
This is what you should do if you want to calculate the best way for your order not to get skipped when it pops up on the drivers app. If you tip well, no driver will skip your order and it will get delivered ASAP.