According to the Fair Labor Standards Act, a US labor law regulating minimum wage requirements, overtime pay, and similar regulations, along with other state laws, you must pay your employees for the time they work — whether they’re clocked in or not. In this case, you must pay them for any time they’re on the clock.
Federal Law on Using Time Clocks Non-exempt employees must be paid for time worked. Time can be rounded up or down to the nearest five minutes, one-tenth an hour (six minutes), or 15 minutes. Rounding time up or down cannot result in failing to pay employees accurately over time.