We are using the Betheme Child theme and our website supports two currencies. The main currency is EUR and the second is USD. Prices for USD are manually set(Fixed). We have regular price and sales price.
By default on currency, switcher USD is selected when a user comes to the website. On all product pages prices(regular and sales) are displayed in EUR and USD without a problem.
The problem comes when the user starts to shop in USD dollars. When products are added to the user cart, the sales price is not used on the cart page. On the cart page, regular prices are used instead of sales price, when USD is selected.
The problem can be bypassed if the user uses EUR for shopping and then when he wants to checkout he switches to USD on the cart page. Then the final sum is calculated using sales prices and everything is displayed correctly.