check out the bulk user manager from www.phdobson.com this allows you to export user records to a csv edit them in excel and then bulk update them back to dnn - if you use a role to place your dummy users into then you can just extract that role to csv - edit them using excell  - take out all the dummy records you do't want to delete then using the bulk manager delete those you do - the bulk manager system access's all the user records ( across all the reevant tables) including profiles
you can bulk modify, create and delete

You could use the exported data to interface directly to your inhouse accounting system with a little bit of thinking and codeing

Excellent module if you handle large numbers of members