What is the ruling on my work as a cashier in a supermarket that sells halal goods, but also sells cigarettes and shisha tobacco, and does this fall under the hadith: "Indeed, Allah has forgiven my Ummah for forgetfulness, error, and what they are coerced into," and what is the authenticity of this hadith?

It is not permissible to directly manage accounts for tobacco, hookah tobacco, or other items whose sale is unlawful, unless one can refrain from these forbidden things and limit oneself to the permissible. Otherwise, it is not permissible to remain in this job.

As for the Hadith (definition), "Indeed, Allah has pardoned for my Ummah their mistakes, their forgetfulness, and what they are forced to do," it is authentic. If the questioner is compelled to work, for example, if he cannot find food or shelter, then he is not sinful for remaining in it until his necessity ceases. He should search for another job.