The only official solution fully supported by Shopify for multiple currencies is Shopify Payments. If a country you are selling in does not support Shopify Payments or for some reason you do not want to use it, there’s another way you can go with to display prices in multiple currencies.
Shopify’s App Store has plenty of add-ons and some of them allow for converting currency. Here’s a list of some of these add-ons we know of:
There are other add-ons providing similar solution. You can search for them on this page.