There is a slight difference, if you capitalize the job titles.
You can easily tell a story about a grocer, a cleaner and an officer without capitalizing their job titles. There won't be any confusion, if you always refer to these persons by the same handle. Readers will think that those are the jobs of these people, but that they have a life and personality beyond that occupation.
If on the other hand you capitalize their job titles, the jobs become their defining characteristic: the Grocer is nothing but a grocer, in all areas of his life. Being a grocer is no longer a job the Grocer has and from which he returns home to be a father and hobby musician, like the grocer, but it is who he is. Depending on your story, the Grocer has either become a depthless persona existing only in the fictional store that is the sole scenery for your tale, or he is a person obsessed with the shelving and selling of food.
If your story is about normal people who just happen to have those jobs, do not capitalize their job titles. If your story is about the personification of officerdom interacting with the personification of cleanerdom, capitalize them.