Currency Conversion Surcharge or Multiplier

[utopiasl]

Hi,

I am using Prestashop 1.4.2
My default currency is NZD, but most of my customers are from US/EU. Therefore I have enabled all major currencies USD/EUR/AUD/GBP in addition to NZD, because they prefer to pay in their own currency. However there is a problem with this setup. As you know banks use their currency conversion rates, which are lower than the official rates given by major currency services like XE/OANDA or Yahoo Finance.

Hypothetically if the conversion rate for NZD:USD is 0.8 in my prestashop, and my product is NZD 100, If a customer pays in USD I will get US$80. But when I convert it to back my currency (NZD) to withdraw it from the bank at the same instant I will not get NZD 100. I will only get about NZD 95. I hope my example is clear to every one.

We only keep about 5% profit margin anyway, so this difference is unacceptable to us. We do not want to increase the price of all items, because then people who pay in my own currency will also be affected.

As a solution I propose to have a currency conversion surcharge; when Prestashop downloads the currency rates, to apply a multiplier (For example 1.05) so that the conversion rate we use is higher than the bank rate. This way in the above example the customer will get the conversion rate of 0.84 and will see the price as USD 84 rather than USD 80. Then I will not face such a loss when converting it back to my currency. People who pay in my default currency will not be affected by this.

I think this should be possible at the point of Currency rate download function of Prestashop, but I do not know which files to edit to get this behaviour.

I would be very grateful if someone can point me in the right direction.
Thank you in advance.
Uditha