AFAIK charging tax on goods bought in another state is against federal law. States charge instead the same tax naming it differently. For instance my state, Illinois, charges "Use Tax" which is tax for using goods bought out of state. Since I don't want to investigate what was bought with or without tax - I elected option to pay flat fee proportional to income. This option can be selected only if there was no big items bought without a tax. Out of State tax can be very messy. Some stores charge tax for items sold to another state illegally, because they have to be authorized, by the other state to collect this tax.
Would you be more likely to buy new gear out of state if there was no sales tax
There is a retailer that advertises in the Absolute Sound that you can buy gear from him without paying sales tax. He is located in Delaware where they don't have sales tax. Being from California that would save me 9.5 percent off the top and that is without even negotiating. I don't know if he charges for shipping or not but it seems like it could be beneficial.