Just to clarify: when most sports fans talk about "tanking", they're not talking about throwing games. You would never get away with that, only an idiot would even hint to his players that throwing games would be advantageous. Mel Bridgeman reportedly did that with the expansion Sens to tank for Daigle and got in serious trouble with the league.
At the management level, there's some evidence to suggest that it may occur. For example, there are 3-4 NBA teams this season that are stripping their rosters bare. They claim it's to create cap room, I call BS...it's to have a shot at landing Andrew Wiggins. Bad NFL teams will often start rookies in the last few games under the guise of "giving them a look". While there may be some truth to that, it also has the desired effect of giving them a greater chance of losing and thus better draft position.
Does it happen in the NHL? Probably not as overtly as those other two sports, but I think it does happen to some degree.