I sell tickets to a go-cart track and we do stay pretty busy usually, but when we're not. I literally just sit play on my phone and stare at the wall.
Ask your boss if there is some additional work that you can do while selling tickets to make the time go by faster
Talk to coworkers and customers, see if anything needs organizing or cleaning, take a food break if you can...? :/
bring a book to read or bring a book to write/draw while listening to music, paint your nails lol