YOUR insurance doesn't cover the treatment. Other policies may...which is why I added the caveat.
In your situation, it might save you some money to seek out a phototherapy provider, rather than using a standard, recreational tanning salon....and have your dermatologist put his recommendation to paper in the form of a prescription.
That being said, given the phototherapy is being administered by a licensed medical professional...the tax you save might be offset by a higher per visit fee.
I'm not sure why you think spray tanning services are adding the new 10% tax, but I've provided you with the link, directly from the IRS, that says the tax we are talking about should not be applied.
If there is a separate, local tax for spray tanning, that is different.
If your tanning salon is applying the 10% tax for a gift card or package that is specifically for spray tanning (and they have to separate the two pieces/amounts, now, by law), they are defrauding you and the federal government. The tax is only supposed to apply to the money applied to bed tanning. Again, the link I provided is quite clear on this. They can't apply the 10% to all the package simply because PART of your package is bed tanning. They can only apply the 10% to the portion of the package that is specifically for bed tanning.
The 10% tax does not apply to spray tanning. Simple as that.