Just like the idea of documenting things is a way to substantiate you are not money laundering, being up front and honest is the best (naïve?) way to address this?

Yes, you actually lose money on each sale because of the transaction fee of merchant account.

Then you get into the area of all these points / cash back - is that taxable income itself?

I got a 1099 from a bank that gave away a kindle fire when you opened an account, made some bill pays.

There was talk years ago - you work for company, they buy your ticket for you to travel for work... you get the miles from the flight. It's really the company's miles / you benefited from earning the miles and that should be taxable in addition to your pay. but I think there was such pushback / tracking that perk / valuing the perk would be unrealistic.

as gov't becomes more revenue hungry (more than now!?) all these points and cash back from credit card companies is income people are earning / gaining and could be something the gov't wants to tax as income. I get a 1099 div for the 1 share of Disney stock each of my kids own. something like $2 a year. postage / admin to mail that form is more than the tax due but gov't makes the companies do it...