Because of the trend in complex local and State sales tax rates cash registers over the last decade and a half started coming out with two tax rates however in the last 5 years or so most are coming out with four as the taxing rules have become even more complex.
I have only helped on customer set all 4 tax rates but it seems like a trend that will will not be able to avoid so when you buy a new cash register make sure it will handle the taxation requirements or your city, State and county.
The most common situation we run into is that the local sales tax will be one rate for hard goods, and another rate for restaurant and bar sales, and another for hotel/motel tax. In these areas many restaurants were surprised to find out that if they sold tee shirts, hats, souvenir glasses etc those items would be taxed at a different sales tax than the food and beverage.
Also in many places things may be taxed unless the consumer is paying with EBT which may reverse the tax status of an item.
So as you can see checking on your local sales tax regulations before you buy your cash register can be worth ding the home work. Find these things out before you buy or program your cash register for sales tax. I recommend contacting your department of revenue and giving them your address so they can tell you the rate(s) you must charge.
I think all the new SAM4s cash registers have the ability for four tax rates and so are the Sharp cash registers.