I suspect tipping uneven numbers will be the norm 10 years from now.

For a long time, we paid with cash, and uneven numbers was standard. Most people don't want to take the 17 cents change, so they leave it for the server, above what they tip in whole dollars.

Credit card tippers usually tip even numbers because people aren't good at simple math (hmmm what's 100 minus 34?).

But, as other have noted here, as the auto-tip functionality becomes more common, it will be uneven numbers even for credit cards. I've noticed it more frequently in taxis now when you pay with a credit card, and are given the choice to push one of three tip buttons, showing %. Interesting, the Uber app bucks this trend and shows whole dollar tip amounts instead...of which the highest choice is always ridiculously high.