Fans and media types talk about tanking. Teams don't.
At the end of the day, the players and coaches are professionals who are playing their job, and many of them have pride in their work.
The closest I have seen to a proper tanking are the Colts, who vehemently deny doing it, and the Browns who after their multi-year long "tanking" managed to add a bunch of near 50/50 seasons, and a, singular, winning season. That's not a winning strategy. It can work, but it is too dependent on luck to really even be considered a strategy.
Teams will throw in the towel for the last couple of games, and start playing down-roster players to see what they have. However, those players are still playing, and the teams are not upset if they win. If they aren't doing that for a couple of meaningless games at the end of the season then they certainly aren't doing it for a full season, or multiple seasons.
Well, unless you are a genius like Andy Reid who managed the incredible feat of "tanking" while going to the playoffs multiple years in a row. Or the Eagles who treated their QBs as disposable, and just threw them away before they cost too much. .... I hope it doesn't need to be said but to be sure, this last paragraph is me making fun of certain people.
Anyone remember the time the Texans signed Brock Osweiler to a 4 year $72 million deal after only starting 7 games, and traded him to the Browns (who then released him) after one year?