I have never seen nettles tea in stores, but maybe I just didn't pay attention (well.... hardly so, but maybe). Anyway, it's not what you can be offered to drink when waiting in a reception room.
Coffee? - Yes/no, thank you.
Tea? - Yes/no, thank you.
Mint tea? - No, thank you, I don't like mint.
Green tea? - Yes, thank you. / No, thank you, I prefer black tea.
Nettle tea? - What??