In which developed countries (other than the US) does the price tag not usually show the final price to be paid?

Canada. The federal government and provincial government each charge a tax which is added to items you buy. The provincial tax is added on top of the federal one usually, unless the province uses what is called Harmonized Tax which combines both.

In Quebec for example we have 5% GST (Federal) and 9.5% PST (Provincial). When you add both, with the 9.5% on top of the 5%, it takes 14.975%. So if you buy something labelled $100 CDN, you will usually pay $114.97.

There are exceptions in which case some items are charged one tax (books for example) or none (food for non-immediate consumption). Rules are very specific. For example, buying 6 food items makes them exempt from taxes because that is not considered for immediate consumption. On supermarket receipts it will be marked F, P or FP depending on which tax applied.

Japan.

After the recent consumer tax hike (from 5% to 8% on April 1st 2014) in Japan many supermarkets and shops show only the price without the tax which is quite regretful... It was very rare practice before the tax hike.

As an addition to the other answers, this can happen even in the EU: If you buy bottled water in Germany, then typically you will pay a depostit for the bottle, which you can return later. Deposits are typically 25 cents/bottle and in some cases almost triple the amount of money to be handed over of the bought good.

This is not a tax, but fits the scope of the question as travelling people often do not return the bottles due to convenince. Price tags often state the deposit in the small print, but they are extremely easy to overlook.