Was I wrongly fired for reporting wrongful activities by a manager?

Tennessee is an employment-at-will state which means you can be fired for any reason and there is no liability for the employer unless there is an unlawful motive for the action taken against you. There are generally only two forms of unlawful motives: unlawful discrimination or unlawful retaliation. Discrimination in employment is unlawful if it is due to race, color, sex, national origin, religion, disability or age 40 or older. Retaliation in employment is unlawful if you engaged in one of a handful of "legally protected" activities and were fired for engaging in that activity. If either of these was the motive for the termination, then you may have a claim for unlawful termination. I do not immediately see any unlawful retaliation although it is possible if what the manager was doing was unlawful in some way.  Paying people for time they do not work or violating company policy, by themselves, are not unlawful therefore reporting such actions would likely not be protected. However, if you want more information and to be able to more fully discuss your situation, you should consult with an experienced employment attorney about this.