Specific Prices on Products based on Currency Choice

[HLD]

Hello all,

I'm still confused as to how to display specific prices according to Currency choice by guest (non-registered) user.

Here are some details to note:

-- Geolocation is OFF (we are not using it)

-- A guest can choose to see our products in 3 different currencies: EUR, GBP & USD

-- Our store's default currency is EUR and based in Spain

-- All currencies are exchanged at 1 because we want to specify our own prices (not use the exchange rate in Prestashop)

-- Taxes & Tax Rules have been created (see screenshots)

When I add a specific prices for a product (see screenshot), the tax rule used is the 21% which is the Europe tax. This works just fine and 'Tax included' message below the price is what we want for those who choose EUR as their currency.

However, for GBP currency, we want the tax to be 20% and the message 'Tax included' as well but if the guest chooses USD, we don't want tax added and the message 'Tax excluded' below the price.

I hope someone can enlighten me on this as I've been racking my brain with this issue.  Why is it so difficult?  Am I missing something? Do we have to have Geolocation turned on?