Tickets and Concession sales tax is calculated differently.
Sales tax is specified for each ticket type. For instance: Adult Price=8.43 Tax=.57
This allows tickets to display the price and tax when printed.
Concession is more complicated unless your are including sales tax in the customer's price. Each state has a 'tax table' that determines how to round sales tax in each transaction. Calculating the tax per item is not valid.
Let's look at an example. At the time of writing the WA 8.4% tax table specifies a tax of
.50 between 5.90 and 6.01 of taxable sales
1.01 between 11.97 and 12.08 of taxable sales
Let's assume a drink is priced at $6.00.
When purchasing 1 drink the customer would pay 6.50 (6.00 price + .50 tax)
When purchasing 2 drinks the customer would pay 13.01 (12.00 price + 1.01 tax)
The second transaction will result in pennies in your cash drawer. This isn't a problem with WA, every state with sales tax will experience pennies in the drawer.
Yes there is a exception to this. If your state has a 10% sales tax, you only sell items priced in even dollars, and the sales tax rounding rules are consistent.