Here is an excerpt that might help.
It is not possible to set up the system to round amounts up or down. The Tax Calculator business function (X00TAX) rounds amounts as follows:
If the least significant digit is 5 or greater, the system rounds up.
If the least significant digit is less than 5, the system rounds down.
For more information please review the following:
JD Edwards EnterpriseOne Applications Financial Management Fundamentals Implementation Guide, online: Chapter 24 - Understanding Rounding Versus Soft Rounding
E1: FIN: How To Understand Tax Set Up Within JD Edwards EnterpriseOne Financial Management (P0022, P4008, P0004A, R0018P, P73GE0) (Doc ID 1413283.1): Soft Rounding for Taxes