I built a similar tool to the OP that implements the same rounding behavior if you’re in the iOS ecosystem — https://apps.apple.com/us/app/synctimer-by-practice

I built a similar tool to the OP that implements the same rounding behavior if you’re in the iOS ecosystem — https://apps.apple.com/us/app/synctimer-by-practice/id1522971001 https://apps.apple.com/us/app/synctimer-by-practice/id152297... One of the main benefits is that it doesn’t require the internet and can synchronize iPhones, iPads, and Apple TV’s using either peer-to-peer WiFi or Bluetooth with no manual pairing. Also had an interval timer for exercises, group activities, etc...