Some will argue you should terminate him saying, “how can you ever trust him?!”
But, if he really is a good employee, why get rid of him. No one is perfect! Can you really trust anyone? Should you trust anyone perfectly?
The employees you need to worry about are NOT the ones you catch stealing ... it’s the ones you don’t catch stealing!!!!
$15 is a small amount (not saying he is justified). Don’t let such a small amount ruin an otherwise good situation.