This is a tax that is required to be paid by consumers who lives in Japan. Since The Yoseido Gallery is based in Japan, 5% Consumption Tax would be applied. If you DO NOT live in Japan, you DO NOT need to pay this tax.
The simplest way to be sure that you are viewing the price that would apply to you is to create a member account. Once you create an account with your correct address information, all you have to do is log into your account when you visit the store and you will automatically be shown a price inclusive or exclusive of the Consumptions Tax, depending on your address.