You can use Dimensions Data Checker to increase the number of decimal places used for Prices, Quantities or Values in the database.
The number of decimal places used cannot be decreased however.
Before you begin, you should take a backup of the database and we also highly recommend testing this on a test database first of all.
Log in to Data Checker
Browse to Data Check, General, Increase Decimal Places
Read the warnings and proceed as necessary
Increase the decimal places for Prices, Quantities and/or Values as required
Select the Green tick
Read the warnings and proceed as necessary