Working after-hours

In the state of Maine, is it legal for an employer to refuse payment for hours worked after the business is closed? The example in question: a friend of mine works a closing shift at a small shop. She is typically there for about one hour after the store closes, to get the store cleaned up and re-organized, but her employer does not pay her for this hour. She refuses to bring this up with her employer, and I'm wondering if her employer's behavior in regards to payment in this situation is illegal. Thanks.