You cannot subsequently use R/3 standard functions to make a consistent change to the number of decimal places of a currency in the R/3 system that is already operatively used because the system interprets all amount values in the database according to the number of decimal places of the reference currency that is defined in the system. Other terms
For a consistent change of the number of decimal places of a currency, you also have to change the corresponding amount fields for the currency. You can do this within the framework of a conversion project with SAP Consulting SLO (System Landscape Optimization).
TCURX, currencies, decimal places Reason and Prerequisites
The basic prerequisite for implementing such a solution is that the number of decimal places was NOT already changed subsequently in table TCURX or that this setting was not yet used in postings. If you have made a change in table TCURX, undo it immediately, since otherwise this change causes serious inconsistencies in the system that can only be corrected with extreme effort and mostly can be only partially corrected. Solution
https://service.sap.com/sap/support/notes/434349 (SAP Service marketplace login required)