Hi Drazen, thanks for raising this question in the Community. I’d recommend to contact the support team and raise a ticket with them. Have a great day! 

Hi Drazen,

I’m sure its a good idea to follow Lily’s recommendation and contact support.

For anybody reading this in the hope to find a solution, I’d like to propose the following workaround for the time being:

Use an extension (or, if possible, a subscription) that is executed on every create or update order event and writes the high precision sum into a custom field. 
Unfortunately, there is no custom field type for high precision money - there is once again only cent precision, so you’ll need to store it e.g. as a JSON String.

I believe there is potential in two easy-to-implement but valuable improvements in commercetools in your inquiry:
1. Add a custom type for high precision money

2. Add a “mode” to orders that will calculate the totalPrice in high precision money

Best regards,
Patrick

Thank you @Patrick Burkart I would agree on the high precision mode on order level. 

Because currently variants support the high precision but a lot of systems need to be in sync also on order level and I know that often there could be rounding issues, especially when some discounts are applied or custom items. 

Regards, 
Drazen