Cost Units
Cost units can be defined company/store/workstation-specifically in Configurations. Defining cost units store/location-specifically is usually sufficient.
Cost units can be viewed under Accounting → Cost Units. It is also possible to define special rules for cost units, if needed. The following rules (in order of priority) are supported:
Sales and Discounts:
Product Category
Product
Payments:
Payment type
Only one rule can be created for a cost unit; however, you can define multiple Values (and Customer Groups, if applicable) for the rule.

Cost unit rule example