I tip any time I'm prompted, and I spend 500 Pokedollars every time (mostly due to my low amounts of money). I found my first two successful RE shiny captures within the span of 24 hours recently- an Axew and a Mime Jr.
3DS FC: 2707-2741-9594 Be warned, I may jump to epic fails of conclusions and general other errors. In advance, I apologise.
I have a routine. I go to 2 cafes, tip 1000 at every option, then go to the Battle Chateau, and tip the maid and butler 1000 each. I've run into 4 shiny Pokemon today and a total of 13 altogether in Y over the past 8 days. I think tipping works but it could just be that the shiny rate is higher in the Safari.