Where to perform calculations

Summary:
Where do you perform calculations for different business processes?

Content (please ensure you mask any confidential information):

We have an existing EBS solution for HR which contains certain custom build calculations, like calculating the bonus payout and commute compensation.

Now that we are moving towards Oracle HCM, what is the best solution to re-build those calculations? Can we leverage out-of-the-box HCM functionality? Use other Oracle solutions like EPM, OIC, OCI?

Curious how you approached this.