Overall, you need to add in the sales tax on top of the price you are charging, so that when you file your state taxes, you can pay the state what is owed. Otherwise, you'll have to pay out of pocket.
For example, if Sales taxes are 5% and your widget is priced at $100, you need to charge the customer $105.00. Because when you file your taxes, you'll have to declare how much money you earned for the quarter or year. At which time, Da Man, will send you a bill for their cut.
First you have to try to get current market rates for your products (after printing). You can look for other marketers prices on which they are selling their products.
Say competitors selling their products on market price of $18, then you can offer yours on $20 because. This is because you didn't have enough volume to sell as compared to established marketers. So selling your products & getting some benefit from it, you have to set your prices ahead of them.
But selling on higher price should not be the fact to standout from the mob, you have to offer something extra in your products like gift hamper, discount etc.