Stop calling them tips, start calling them commissions on sales, and automatically include that in the price of each item. This eliminates tipping entirely and

Stop calling them tips, start calling them commissions on sales, and automatically include that in the price of each item. This eliminates tipping entirely and if the customer doesn't like the quality of service, they can make their displeasure known by not returning. Nobody working in high-end retail sales gets tips, but they do get commissions, which are included in the listed prices. This is really a much better, fairer, and less socially awkward approach to the issue. Note it's also much better than replacing tips with an hourly wage increase because the staff is rewarded if the business is busy, so they're incentivized to keep the clients coming back.