Ensure that all the values in the column are based on the same currency by selecting a specific currency format for the column. The dropdown box offers over 100 country choices so you can specify currency in most local formats in column settings.

Reference:

• https://support.office.com/en-us/article/list-and-library-column-types-and-options-0d8ddb7b-7dc7-414d-a283-ee9dca891df7
• Create currency field using code