Gordon, I think you are talking about the contacts/members import. There is no import for transactions - which is the topic of current thread.
In my mind, providing an option to delete specific transactions (via import or otherwise) is not a good idea from audit trail/accountability standpoint. I think what's needed is two things:
1) Ability to delete all transactions, e.g. after testing period
2) Ability to void specific transactions, e.g. to fix mistakes. These should still be accessible in the list but voided in reports etc.
Dmitry Buterin, Chief Apricot