Sales tax can vary greatly between states, counties, even towns / cities.
Tax rates also differ depending on the item.
For example in some places Subway untoasted is considered a grocery item, taxed at 0% but toasted it is a restaurant item.
Clothes in some states are taxed, other states have no tax at all.
For example the tax in Los Angeles is different than the neighbouring Orange County.
Given the fact sales tax is added at the till it would be good if Monzo could help us estimate tax before deciding on a purchase so we can stay in budget.