I have worked (and am working) a lot with currency exchange. I see in the forum that Wix users now start to use it too, with the standard currency exchange functions built into Wix Stores.
One word of caution: THE exchange rate does not exist. Every currency has many exchange rates against the same target currency (bulk buyers, consumer bank rate, it differs really per country) and, to make things worse, it really depends where you get this exchange rate from: Tokio is different from New York, is different from London, is different from consumer bank A, credit card company B, and so on.
But wait, there is more: every currency has a Buy and Sell quote. WHO is buying differs per provider: one provider might express BUY as “the bank is buying/you are selling”, the other one as “you are buying, the bank is selling”. Huge difference.
Also, some providers, like XE.com, calculate a mid-rate (an average across many banks/markets/other providers) concerning buy and sell prices, and then the average of those 2. But it is a rate that does not exist, which nobody can get.
In short, when you start doing currency conversion, make sure you state everywhere that actual amount may differ (slightly) from the displayed converted amount (and with larger amounts, the “slightly” can become enough to buy some beers), UNLESS you guarantee the converted amount (which is very dangerous for some currencies, especially over a longer period).
Example: I live in Argentina. Argentina has, as of last count, 12 rates against the USD internally. If we compare 2 (the official one from the BCRA and the one from Western Union), there is more than 65% difference between them. And if people from Argentina buy something from outside Argentina, the official rate PLUS 30% is calculated. But no bank states this in it´s rates, you have to know.
So in short, if you start doing currency conversions, investigate your currencies first (especially outside the well knowns like USD/EUR/GBP/YEN). If not, you might be in for surprises.