Zehntar
Enthusiast
Silver Level
I'd probably try and mention it in a joking way to make everyone aware of the error, but keep it as lighthearted as possible. Something like:
"Woah, I think you got a little too much change for that $25 chip. Someone cut off this guy's alcohol, he can't count when he's buzzed!"
It would probably be best to say this while he still has the change in his hand and before he puts into his own stack, because that would be hard to prove. So watch him grab 5 $5 chips, then when he grabs the 6th one, say it. You want to make sure everyone at the table sees that the player had indeed grabbed one too many, but you don't want to come off as you're blatantly accusing him of cheating.
Then if it continues, I might even make a joke about how frequently the guy is getting change during the night. Again, in a jokingly way.
"Hey, that's the 5 time you've gotten change for a $25 chip tonight. We should just give you stacks of $5 chips and make it easier for you!"
Again, you're not blatantly accusing him of anything, but maybe this might get the other players to notice that a) this player does get change a lot and b) he was already caught getting an extra chip, so maybe they'll pay more attention.
Finally, if you don't want to say anything outright at the table, maybe talk to the host about making it a rule that when you get change, you have to have someone at the table agree that the correct change is made before you stack the chips.
I like the the whole idea about joking it off, like calling him out for drinking a bit too much and that he can't count for sure, hehe.. probably the best way to go about it, except for maybe quitting.