Tax Exemption Option for Churches, 501c3, etc

Through looking at some of the forum posts it looks like taxes are a difficult topic through the squarespace interface, but this is a slightly different question.

I'm working on a website for a client who sells bibles and church supplies, so most of their clients will be tax exempt. What would be the best way to attack this knowing squarespace has so many issues with taxes to begin with.

Is there even a solution as of now that can help with this complication?