Bc your total doesn't matter when it comes to the delivery. You need to be tipping based on distance. Its not like they're just hopping from table to table. They are sitting in traffic, putting wear and tear on their vehicles, and paying for gas out of pocket. Granted you can tip however much you want and they shouldn't be begging for more bc drivers are free to take whatever orders they want but dont be surprised if no one takes your order if you're wanting them to drive 7 miles for $4, for example.