Can I sell to my customers in their own currency when my supplier charges me in a different one?

Yes, in most setups you can show prices and take payment in the currency your customer is used to, even when your supplier bills you in a different one. The system applies a conversion rate to the supplier fare and shows the customer a single amount in their own money, which they pay through your normal payment gateway.

The part that needs care is the rate itself. Exchange rates move, and the rate you showed at the moment of booking is not always the rate your bank or your supplier settles at later. Most travel businesses handle this by building a margin into the rate they publish, so an ordinary daily movement does not eat into their profit. Whether that rate refreshes automatically or is one you set by hand depends on your plan and on the rate source connected to your account.

Settlement is a separate matter from display. Your gateway pays out in the currency of your merchant account, and if that is not the currency the customer paid in, the gateway takes its own conversion and its own fee before the money reaches you. Your supplier still invoices you in their currency on their own cycle. Those two conversions are why the amount landing in your bank rarely matches the invoice exactly.

Before you turn on a new selling currency, check with your payment provider which currencies your merchant account can actually settle in, and agree with your supplier which currency your invoices will arrive in, so your accounts team has something predictable to reconcile against.