Again, no one will save money. Say the tax was $2 on a pack of diapers. No tax now, companies/retailers will raise price to where it was post-tax knowing they can get it. There is no incentive for the manufacturer/retailer to curtail sales price.
The profit margin does not change for the manufacturers and the market place competitive pressures still exist. Why would they raise prices when their ROI will actually arguably increase, because more people may buy items that they otherwise would not?