As new technology adds to social pressure, this modern guide to tipping reveals how to approach gratuities for everyone from your barista to the car mechanic. Tipping has long been a tricky topic, but in recent years, the practice has taken on a whole new level of complexity.Service providers are not only increasingly soliciting tips, but they’re also spinning around touch-screen card readers with suggested percentages that can run as high as 30%. Adding to the struggle are bills with a “service