Custom field decimal 4 places

Summary:

we have a custom field of type decimal and currency. How do we allow it to have 4 decimal places rather than 2 (which taleo automatically do).

Content (required):

when we enter 34.5648 , taleo saves it as 34.56 instead of 34.5648

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):