Federal law does not require rest breaks, but breaks of 5 to 20 minutes that you do get count as paid work time (29 CFR 785.18). Your employer cannot clock you out for them.
Some states require them. California, Colorado, Nevada, Oregon and Washington require a paid 10-minute rest break for every 4 hours worked, and Minnesota requires 15 minutes within each 4 consecutive hours.
What you are owed for a missed rest break depends on the state. California owes an hour of pay per day; Colorado owes 10 minutes of pay per missed break. See break premium.
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