I live in a country where the VAT is 25%. If I want to know the VAT of a price I just divide by 5 (the price is 125% of the untaxed price so I need to divide by 5 to determine how much 25% is). By law you always have to provide the price including VAT to consumers so people are aware of the actual cost.
This VAT has not changed for a very long time but if it were to increase (perhaps for good reasons) there would be an outrage. This tax is not being increased without people noticing.
On the other hand decreasing VAT is also not going to happen (even if it might be beneficial). A single point decrease would create a huge budget deficit that would be really hard to cover by other means.
In Japan pre VAT prices are regularly advertised to consumers. In Denmark receipts shows percent and nominal VAT of every purchase.
There is nothing defining to sales tax that makes it impossible to have sales tax and requires retailers to advertise post tax prices.
Sales tax, on the other hand, is more salient because product prices are typically shown pre-tax. That means that when you buy something, you know how much of your money is going to sales tax, and people would realize if all of a sudden their $10 purchases were costing $12 with tax instead of $11.