Apparently it just changed here in Georgia several months ago-now cashiers must have the customer show ID for a purchases of cigarettes (including vape products, but we sell very few of those.)
In California, you have to be 21 and show ID for tobacco products. In addition, if the cashier is under 21, they cannot scan tobacco per the state's rule. So when I was in the checkstand I had to have a manager come and ring up their cigarettes.
In WA if the individual looks less than 27 years of age ask. Once the cashier asks the client has to legally provide it if they choose not to regardless of client age they have to provide it. Even if they're a 50 year old being a d*ick about it. The only time I don't ask is when their face is riddled with age i.e.e wrinkles or grey hair. Otherwise always ask.
In Tennessee you have to ID everyone for alcohol regardless of age, but you only have to ID for tobacco if they look under 27. You also only have to be 18 to SELL alcohol or tobacco. Things vary wildly from state to state.