If you have a transaction date field that you can add to the report, you can add a formula on that field: max(?)
This should give the record that has the most recent date, but it will group by all other fields in the report. If all your other columns in the report are unique per customer then this should provide the results you are looking for. If you have other fields such as a status fields for example and transactions are in different status states you would need to use a different method. If this is the case let us know by providing us with some sample data and we can help you from there.