The US federal income tax is a progressive tax, the higher the income, the higher the tax rate. Some states in the United States are still under their jurisdiction, adding a sales tax of about 7% to the price of most goods sold. If sales tax is also regarded as a form of income tax, then this tax is against the principle of progressive; the lower the income, the higher the tax rate.
meant to illustrate:
In fact, the money people spend on shopping is basically the same.