Seeking solution to avoid roundup in Oracle forecast calculations.

We are aiming to achieve an integer value for the output of 'Final Bookings Forecast'. However, when using the expression round(custom_measure, 0), Oracle is performing a roundup, which results in an unacceptable difference for us.
For example, 5000 is being rounded up to 5032, whereas the acceptable value is 5000 due to the presence of a few high-cost items in the inventory.
How can we resolve this issue?