How to round up the value till specific decimal digit in onFieldValueChange action chain.

Summary:

After calculating the value returns till 6-7 decimal digit. We want this to limit the decimal digit till 3-4. How to Round the calculated amount in below code snippet

Content (please ensure you mask any confidential information):

We have requirement to limit or round the result till 4 decimal places. Please give suggestions how it can be done.   

row.MarginPercent_c = (row.Margin_c / row.UnitPrice);

eg. if above expression returns result as 3.45659933% we want it as 3.4566%

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

23D

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

    if (event?.modifiedField == "CostAmount") {