5.07-09 Avoid using a Top Level for large lists of transaction data

Don't create a transaction list with a top level.  The calculations will need to sum for all items in the list even if only a single item is added

Exception:
5.07-09a Check totals: If a check total of all transactions is needed, but again using the flat attributes modules is preferable

Related to Rule:
5.07-10 Add intermediate sub totals to transaction lists

Best Practice article:
Top Level Item and Parent Hierarchy