Follow bellow steps for work Multiple currencies on your store
Step 1 :
From your Shopify admin, go to Settings > General.
Step 2 : In the Store currency section, Click on Change Formatting.

Step 3 : Find the HTML with currency and the HTML without currency formats: Update below fields
HTML With currency to –> <span class=money>${{amount}}USD</span>
HTML without currency to –> <span class=money>${{amount}}</span>
In each text field, copy and paste <span class=money> in front of the formatting text. Click Save.
Note: Do not put quotation marks around the word money in the span tags. Adding quotes will break the code.