Please let’s stay on topic.
1) real brisker the issue here is to tip or not to tip.
2) is tipping mandatory
3) is it false advertising to lable yourself “free shipping”
4) even if there is an obligation to tip how much
5) where does the root of tipping (mikar) come from.
I would like to start out like this. Many years ago when i played monopoly and landed on a space that would cost me $4 or $8 etc. my father taught us the give $5 or $10 and say ” keep the change and be gezunt!”
Now there was no reason for this other then imparting a value le lesson in tipping. Or more precise showing true hackers hatov.
When I we t to modells with my father to buy a basketball hoop. The schvartsa put it into our van. My father gave him $3. I asked him why there was no rule/sign stating a need, he replied “make a Miesian hashem they know were Jewish. “
When I went to Petra in Jordan they offered me a free horsebackring ride to the city! Of course I took it. When I got there the guide stuck out his hand – tip?
I told him you said free!
There are many times in life that logic declares one way bit practicality says another.
See coffeeroom under tipping before chugga
In every situation a different thing is correct.
I feel you should have not only let him keep the $3 but given him $5 more.
Ps my grandfather was very makpid on tipping goyim, they hate us, let’s not give them more reason.