sales taxes on digital products

1.5.4, php 5.6.4

client is charging sales tax (flat rate on all states) but taxes are not being charged on digital products. I've never even noticed if they are normally charged sales. Each product is listed as taxable with normal shipping rules.

So I just need to know if it's possible or is there any settings (which I have examined thoroughly) that could prevent/enable it?

Or would upgrading make a difference? Since the server she's on is good and still allowing that php level, she has no desire to upgrade.

client realized she didn't need to tax the downloads by her state rules.

My thought was always that since shipping isn't triggered on these products, they can't be charged sales tax because of the way zen cart operates.

There are states that do require sales taxes on these products so this is still a legitimate question.

What payment method is in use when the tax isn't applied?

both - square and paypal