When we had our 4-plex, we processed internet ticketing at the boxoffice. The customer handed over his credit card or the pre-printed reference sheet, and the printer spit out the ticket(s) immediately.
However, if you had any volume at all (we didn't), you might want to go the kiosk route. That would keep those customers out of the boxoffice line altogether.
Locally, the kiosk printers use a paper with a different tint than the boxoffices use. That alerts the usher to pay attention to whether the customer paid for the proper tickets (age levels, ratings, etc.). That would head off most problems, other than the up-front expense of the kiosk.
The administrator has disabled public write access.