Hi Tom,
Thank you for considering our plugins for your project! To answer simply, yes. Let’s say you’re using WooCommerce as your ecommerce provider. If you have taxes set up, they will be added to the ticket as they would a physical product. No tax will be added to free tickets. I quickly created a test event with a free and paid ticket and have added both tickets to my cart. See the screenshot below for a visual example:

You can also edit the ticket via WooCommerce (just as you would edit a product page) and it’s tax-related options:

Please let me know if this helps answer your question and feel free to reply back with any additional questions you have. I also recommend reading over the New User Primer: Event Tickets & Event Tickets Plus tutorial to get an idea on the process of installing the plugin, making tickets, managing your orders and attendees, etc.
We offer a 30-day money back guarantee allowing ample time to test the plugins out to ensure they meet your needs. Thanks again and enjoy the rest of your day. Cheers!