I am an author who sells small quantities of my books at presentations to groups. Am I responsible for collecting and filing state and local sales taxes at each location in every state where I make in-person sales?
The answer depends on each state where you are selling your books. There are states where a temporary presentation and sales event is considered nexus for sales tax purposes, obligating you to collect and remit sales tax in that state. You would need to review the nexus rules in each state you visit to determine if your event, likely quantity of sales, etc will result in a requirement to collect sales tax. If so, in most states you will be obligated to register with their department of revenue in order to collect and remit sales tax. Check out this article on Sales Tax Facts for Book Authors for more detail.
Each state has different sales tax rates (a few have no sales tax) and many of these states also allow localities to charge additional sales tax up to certain limits, so the process of determining the appropriate sales tax rates for multiple sales locations can be tedious. Sales Tax Institute has a helpful list of sales tax rates by state along with the range of local tax rate additions, but you will still have to go to a particular state's department of revenue website to determine the appropriate local rates to charge for a particular sales location.