Inspired by this question, I started wondering about how voluntary tips are taxed when they aren't on a service, but on goods.
For example, here's an interesting one. There's a legit company called EmeTerm (https://www.emeterm.com). They sell medical electronics devices online and allow customers to add a voluntary tip to their purchases. How are those tips classified for tax purposes?
Would this be classified as general revenue, or classified differently?
Interested in answers for all jurisdictions (just using EmeTerm as an example).