Sales tax is typically only collected for physical products that are shipped, so you should select YES to charge sales tax on products like this.
Service oriented products such as Workshops are typically not subject to sales tax, so for products like these you should set NO for the tax setting.
Digital download products are taxed in some states but not in others. Refer here to find out if your state charges for digitally downloaded products.
Of course if you are not charging any sales tax at all in the cart, then none of this matters. See the Settings > Sales Tax Settings page to configure whether or not you want to charge sales tax on your prints and products.