You may charge for a tour that features liquor samples, so long as the price is proportional to the volume of liquor samples. You are required to establish your set price for a tour that offers a 1 oz. liquor sample, then use that rate to determine the charge for a tour that offers liquor in excess of 1 oz.
For example, if you establish that the charge for a tour with a 1 oz. sample is $10, then the charge for a tour that offers 4.5 oz. in samples must be $45.
Tour samples may only be offered in the following portions: 1 oz., 1.5 oz., 2 oz., 2.5 oz., 3 oz., 3.5 oz., 4 oz., or 4.5 oz.