Yes, I believe it is customary. It is subjective though. If 2 guys are dropping a dryer in my driveway, that I'm going to move inside and hookup myself, I'll only juice em a 5 each. If they bring something and make it "turn key" then I do the 10.

I juice the cable guy a fiver if he has to come out for something too. Last time he went back up on the pole and fiddled with some wires to get me a little quicker internet connection. Another time the guy gave me about 30 feet of coax in case I wanted to change how I had shit hooked up.

I usually don't juice business owners. If I have a construction guy or plow guy come out and it's him and a helper, I'll offer coffee or a drink, but they are already making profit. I pay them in cash, so they can consider that their tip.