this service is not available at my home but if it were-
may not be a popular opinion but i don't see this job as different from any other
walmart employee position and i don't tip the person stocking the shelves, the person who brings my order out for pick-up or the cashier at the register so i would'nt feel obligated to tip a driver that drops off at my home (esp. if i'm charged a fee for it). if it's a contracted company i feel even less obligated b/c they are not the ones who gathered and put together my order.
disclaimer-i live in a state where there's no difference in tipped and untipped minimum wage. i might feel differently if that was not the case.