Note: Rounding rules that are configured on usage rates are in use and cannot be deleted (the delete action button will be greyed out in this case). In order to delete a rule in use first check the References tab on the Edit Rounding Rule panel to determine which rates are configured with the rule. Next, proceed to modify the usage rate to use a different rounding rule.
Select the entry on the left under the Rounding Rules heading or use the Filter text box to narrow down the list
On the left under the Rounding Rules heading click the icon
On the confirmation dialog click Yes to confirm that the selected rule should be deleted