All the state lotteries I know of also pay smaller prizes for tickets which match some, but not all of the numbers. One state used to give a free ticket for matching three-out-of-six, and cash for matching four- or five-out-of-six. I don’t know the formulae used to determine the amounts.
To calculate whether it would be a worthwhile wager to buy every possible ticket, you’d need to know how many other tickets were sold (to know the chances of splitting the prize with other winners), and add up the expected payoffs of all your winning tickets. If you really want to be precise when you figure the odds, the math would get very hairy indeed.