[woodruffw]

In principle: the money goes completely to the employee(s) being tipped, so it doesn’t make sense to tax the business for money it doesn’t receive.

[Ekaros]

Why should that matter? Let's say you run software consulting. And most of the price goes to labour. Would that not mean that sales tax should only be applied to part going to business itself?

[woodruffw]

Because sales tax is a tax on a sale, not on your employees' wages. Payroll and income tax (among others) apply to wages.

Whether payroll tax applies to tips depends on the municipality, but income tax always does.