Including Taxes in the Posted Price

In Colin Grey's video Death to Pennies he mentions how it is absurd that we do not include tax in posted prices at stores. As a result of this oversight individuals are unable to efficiently use their change to pay for items. My problem is with inefficiency of the whole affair; calculating the tax one time when marking the price on the shelf as well as the price being constantly priced and repriced in the heads of the customers and then recalculated again at the register. While the register does that instantaneously we humans tend to struggle even with the most basic of math. The result must be lost time, more stress and I would assume lost sales.

I think the excuse that if we include the tax in the prices people will be dismayed by the higher prices. I is exaggerated. Individuals take tax into account when making a purchase so why would they not switch from expecting tax to expecting higher prices?