Tickets are 1 ticket for $15, 2 tickets for $30, 3 tickets for $45, 4 tickets for $60, 5 tickets for $75, and the 6th is free with the 5th ticket contribution.
So, if you contribute $100, you will get 7 tickets. If you contribute $105, you will get 8 tickets, and so forth... $150 you will get 12 tickets!