This is a simple thing to do with other workflow products, but I can't seem to find how to do this with Nintex
Teddy, Please expand on your question just a little bit so I can better understand where you need to display a currency value. You mention through a workflow product, so I wasn't able to determine when you were using the value.
For list display or form display, if you use a SharePoint field of type Currency, then the decimal, separator, and symbol will be added automatically in the formatting.
When type currency is selected you will see the below options.
This isn't working on my form. I have currency fields and in the Nintex form, the currency symbol and the comma separation is not occurring.
Are you talking about on the Edit form? While a field is editing the formatting is not applied.
In the display mode, you should see the formatting.
I have tested this on both Forms for O365 and on premise versions of Forms.
I can confirm that the currency field does not in fact display as currency on edit on both versions and you will need to apply custom java script to do so. You can find references online on how to apply custom java script to a field to change the formatting to currency on edit. Alternatively you can make a feature request to have this piece added to the product on our user voice site here: Customer Feedback for Nintex
However, on display I can confirm that it does not show a dollar symbol nor decimals and commas UNLESS you specify a number of decimal places in Office 365. In on premise versions it is displaying the currency field as expected on display mode as Andrew is seeing.
Here is the configuration for my column on my list (O365):
Here is the result:
When you change this from "2" to "automatic" you receive the following result:
I am currently investigating internally if this issue is a bug or a future implement for forms for O365.