When to tax for T-shirts and Accessories Sales

[DutchyTown]

I’m based in Pennsylvania and sell T-shirts, mugs, face masks, art work and other accessories online to the local community. How do I figure out when to charge sales tax?  My site seems to automatically be charging PA sales tax and one customer asked me why.  Not sure if sales tax should be charged and why my store is automatically setup to do so.  Can anyone guide me on this?