I would say in simplest terms, 'it depends'. Typically in my state, they charge sales tax based on your home location. While that sounds confusing, different cities/areas have their own sales tax on top of the state sales tax. Texas has this type of varying sales tax locations, base is 6.25% with some locations having a 2% additional fee.
Since you mentioned Texas, there is a Sales Tax exemption form, so if you are listed as a out of state resident, which you should be, you are exempt from Texas sales tax. Here is a link to the webpage for that form:
https://search.comptroller.texas.gov...hicle+purchase
Montana is a well known, no sales tax state, and many people list it as their place of residence - but make sure you meet those residency requirements, and as non-US citizens, it might have other implications, but we'll assume you know and have research those items.
Enjoy the site seeing!