To calculate the sales tax rate, you can use the formula:
Sales Tax Rate = (Sales Tax Amount / Price of the Item) * 100
In your case, the sales tax amount is $0.91, and the price of the compact is $13.
Sales Tax Rate = ($0.91 / $13) * 100
Sales Tax Rate ≈ 7%
So, the sales tax rate for the $13 compact is approximately 7%.