Back in my high school days, I worked at a restaurant as a waiter (cough "server", being more polite/correct), and always hoped people would leave the tip in cash.
You had the option at the end of the shift to punch in a total for your claimed tips. There are pro's and cons to claiming cash tips -- Pro's being it keeps your actual income on the books, making you more attractive for loans/financing. Con's are you get taxed more.
You get the money either way at the end of the night, but the tax man was not kind to you at year's end with all those claimed tips.
(Yes, this is a different definition of "taxable" than an accountant, wed to prescribed rules, would use. This one describes reality)