This really is a easy report for ShipStation to add to our reports. All the data is already in the cloud and there is already a field called "Tax Paid". We just need a query setup to get the data.
I do quarterly pre-payments for sales tax in CA, so I would love something simple to allow me to quickly find the dollar amount for a given period. It could be in the settings; put your nexus state in, sales tax rate, done. After the year closes, I can use the existing reports to clean up and tighten the data behind the pre-payments.
It seems like quite a few people have asked for this feature. I wonder why they are dragging their heels. They already have sales by country. It would be a very similar layout.