This is a question many Christians struggle with because they feel convicted that by working in a store that sells alcohol and tobacco, they are in some way encouraging or enabling others to sin by drinking and smoking. While the Bible is silent on the subject of selling alcohol and tobacco, but there are scriptural principles that can be applied to this question.
Many people believe smoking cigarettes to be sinful in the respect that it is being willfully harmful to one’s body. However, overeating, which is much more prevalent than smoking, at least in the U.S., is just as sinful, if not more so because of the biblical commands to avoid gluttony (Proverbs 23:2, 20). Does this mean that restaurant waiters and fast-food employees are causing others to sin by selling rich, fattening foods to them?
The question of alcohol is a little different. Drinking wine and/or alcohol is not identified in the Bible as sin. The sin is being “drunk with wine, in which is excess” (Ephesians 5:18). Consider that Jesus Himself drank of the fruit of the vine, and Paul recommended drinking wine to His student, Timothy (1 Timothy 5:23). It is the responsibility of the users to determine for themselves where they need to stop drinking, and as such, the responsibility for drinking lies with the drinker, not the supplier.
To be sure, in some situations, where a person is obviously already intoxicated, or situations that break the law, clearly it would be wrong to sell alcohol to a drunken person, or to sell alcohol or tobacco to minors. However, in the day-to-day work environment, selling alcohol is no more sinful than working in a grocery store. But aside from these circumstances, it is the responsibility of the drinker to regulate his/her intake, not the seller. It is also the responsibility of the individual to decide whether smoking or overeating is detrimental to their health and to act accordingly.
In short, while there is no scriptural mandate against selling alcohol or tobacco, there are definitely things to consider that may make it a wrong choice for a Christian to work in these environments. If one feels convicted by the Holy Spirit about selling alcohol or tobacco, perhaps the Lord is speaking and it is time for a career change. Christians should act according to their faith when it comes to matters such as these, relying on our consciences to approve or not approve of our actions. Paul addresses this same principle regarding whether it was proper for believers to eat food sacrificed to idols: “Blessed is the man who does not condemn himself by what he approves. But the man who has doubts is condemned if he eats, because his eating is not from faith; and everything that does not come from faith is sin” (Romans 14:22–23). Ultimately, the decision should be made with prayer for wisdom, which God promises to grant to all without finding fault (James 1:5).
 Got Questions Ministries. (2010). Got Questions? Bible Questions Answered. Bellingham, WA: Logos Bible Software.