I'm not familiar with the tipping system in the US. One day I'm buying a coffee and i am presented with a machine asking me to tip 15%, 18% and 20% and no tip. I feel like I have to tip at least 15% but i still haven't tasted the coffee and I won't even sit down at the place. I don't mind tipping if I get some sort of service.
What do people do with the tipping for getting a to-go coffee?
In general in the US, the 15% guideline only applies if you're getting some service associated with your food/beverage - service in a sit-down restaurant, food delivered, etc.
If I'm getting coffee to go and paying cash, I'll usually throw some of the coins I get in change into the tip jar, but that's as much because I don't like carrying coins as anything else. (The largest commonly used coin in the US is only worth $0.25.) If I'm paying with a card and presented with those options, I'd skip the tip.
