Currency Signficant Digits for Email Template

I have an email template that sends an invoice & uses the variable $aos_invoices_total_amount.

The significant digits are set to 2 (in the user settings locale) for the user who created the invoice, created the email template & sending the email. However, it displays at 100.000000.

I know how to change this with printf in php, but I don’t know where to use the php to do this.

Does anyone know where I can look to make this change?