This is reinforced in the movie by the title cards, which share themes with the book. Some of them describe sins (vagary, malaise), or judgment (vilification, purgation, perspicacity), or are biblical in nature (harbinger, lamentation, catharsis). Dante's trip into Hell takes in all of the Seven Deadly Sins. Dante's day at the Quick Stop isn't much different. The nine circles of Hell are Limbo, Lust, Gluttony, Greed, Anger, Heresy, Violence, Fraud, and Treachery. All of these are covered in the film.
Limbo: Dante's life. By remaining a clerk and doing nothing with his life he is stuck in a perpetual limbo of his own making.
Even the black and white reinforces that.
Lust: Randall watching hermaphroditic porn, or Dante yearning for his ex-girlfriend, or finding out that his current girlfriend has sucked 37 dicks, or ... well, pretty much every second of the movie.
Gluttony: The hockey team consumes an entire drum of Gatorade.
Greed: Randall refuses to cover for Dante when he leaves for a funeral, even though he didn't know the girl personally -- he just doesn't want to miss out on "the social event of the season." Not to mention the running gag about the tobacco company being a greedy corporate machine intent on murdering its customers.
Treachery, Anger, and Violence: Dante loses his s**t at Randall in the end (for telling Veronica that he wants to be with Caitlin) and tries to throttle him. They destroy the whole store in the process.