Is it permissible to donate money taken secretly from its owners—even if the amount is negligible—on their behalf to clear one's conscience?

It is not permissible to take people's money without their consent. What has been entrusted to a person must be returned to its owner if the owner is known, as the Prophet (peace and blessings be upon him) said: "Indeed, your blood, your wealth, and your honor are sacred to you," and "The hand is responsible for what it has taken until it returns it." Taking money without the knowledge of its owners is treachery and deceit. A Muslim must know that his sustenance is guaranteed and he will receive it through a permissible means.