A man from Nelson won $100,000 recently when his numbers came up in the lottery, and he'd purchased 12 tickets with the same numbers. Although this is touted as a lottery tactic, in the long run, on average, people using this method to play the lottery will win less than others, as any wins they have will result in a lower payout per ticket.
For example, if we only think of the jackpot, buying 12 tickets with the same number will result in a 1 in 3,838,380 chance of winning an average $1 million payout, whereas buying 12 tickets with different numbers will give you 12 times that chance, or a 1 in ~300,000 chance of winning - much better odds.
For smaller prizes, there's a set amount to win - and so if you have multiple tickets with the same number you will win a larger percentage of any particular win, but it will be less than you would win if you had 12 wins on a single ticket on 12 different occasions. Both are just as likely to happen, but the one where you buy 12 tickets with the same number makes the amount you win for each ticket less, as for each additional ticket that shares the win the amount per ticket is less.