Praise be to Allah.
There is nothing wrong with working as a security guard in a supermarket, but if this store sells haraam things such as alcohol and pork, it is not permissible to work there either as a guard or a cashier, because that implies approval of evil and because of what you mention of helping to transport it. This is emphatically forbidden because of the report narrated by Abu Dawood (3674) and Ibn Maajah (3380) from Ibn ‘Umar who said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Allaah has cursed khamr (alcohol) and the one who drinks it, the one who pours it, the one who sells it, the one who buys it, the one who squeezes it, the one for whom it is squeezed, the one who carries it and the one to whom it is carried.” Classed as saheeh by al-Albaani in Saheeh Abi Dawood. For more information concerning the ruling on carrying and transporting alcohol for someone else, please see the answer to question no. 96739
Based on that, you should look for a job that is befitting for the Muslim who is proud of his religion, follows its commands and heeds its prohibitions. You should take measures to find permissible ways of earning a living. Allah, may He be exalted, says (interpretation of the meaning):
“And it has already been revealed to you in the Book (this Quran) that when you hear the Verses of Allah being denied and mocked at, then sit not with them, until they engage in a talk other than that; (but if you stayed with them) certainly in that case you would be like them”
“And when you (Muhammad SAW) see those who engage in a false conversation about Our Verses (of the Quran) by mocking at them, stay away from them till they turn to another topic. And if Shaitan (Satan) causes you to forget, then after the remembrance sit not you in the company of those people who are the Zalimoon (polytheists and wrongdoers, etc.)”
[al-An ‘am 6:68]
“And those who do not witness falsehood, and if they pass by some evil play or evil talk, they pass by it with dignity”
Shaykh Ibn Baaz (may Allah have mercy on) said: “Falsehood” includes all kinds of evil. That includes shirk (associating others with Allah), kufr (disbelief), the festivals of the mushrikeen (those who associate others with Allah), gathering to drink alcohol and smoke, songs, musical instruments, movies and other evils. Something similar was stated by al-Haafiz Ibn Katheer in his commentary on this verse.
End quote from Majmoo‘ al-Fataawa, 27/429
Shaykh Khaalid ibn ‘Ali al-Mushayqih (may Allah preserve him) was asked about working in the management of a hotel that sells alcohol. He replied:
There is no doubt whatsoever that the one who welcomes guests in such a hotel and prepares accommodation for them is a partner in that sin. I advise the brother to keep away from that and to try hard to look for permissible work even if it brings a lower income.
“And whosoever fears Allaah and keeps his duty to Him, He will make a way for him to get out (from every difficulty).
3. And He will provide him from (sources) he never could imagin”
He should try hard to look for permissible work and when he finds that he should move to that job.
End quote from a fatwa by Shaykh Khaalid ibn ‘Ali al-Mushayqih (on the Internet).
For more information please see the answer to question no. 96739
To sum up, it is not permissible for you to work in these and similar places even if you need to work. For more information please see the answer to questions no. 82886 and 31781
You have to offer a great deal of du‘aa’ (supplication) to Allah and beseech Him, for He is the One in Whose hand are the stores of heaven and earth and He is able to help you and make things easy for you.
For more information on the means that help to bring a response to du‘aa’, please see the answer to question no. 5113
And Allah knows best.