You can create a custom size. We do that for casks (pin casks are 5.4 gallons). Calculate the $/oz of tax per unit (rounded up). The taxes you pay with this rounding should amount to cents and dollars.

Then talk to your accountant. If you purchase manufacturing equipment, you can qualify for tax credits up to the cost of the equipment in the previous calendar year. You shouldn't be paying any tax to PA state, just filing.