What jobs could I do to help get me into the civil engineering field?

A couple of thoughts on this. In the public sector (state agencies, utility companies, municipalities), there would be plenty of options for non-civil engineering related jobs. Anything you could learn about how public agencies work and function will be helpful to you as a future civil engineer. Things such as "how do they fund capital improvement projects", "who/what/when/where/why do they decide which projects to fund", "process for decision making", "approval/permitting processes", etc.

In the private sector, same thing would apply of gaining knowledge on how the professional workplace operates and gains business. This could be done through internships or non-engineer positions such as CAD technician or administrative/team assistant. Be a curious person, ask questions, seek to understand, and get coaching and advice from the civil engineers on a path forward.

When we interview candidates for entry level positions, we are looking for people who are eager to learn, ones that are "teachable" and "coachable". Someone who has experience in customer service such as yourself being a cashier, would be highly likely to be viewed as favorable because you most likely have learned very valuable lessons in pleasing a customer and being pleasant in uncomfortable situations. Keep these things in mind if you interview at places. Talk up your experience in dealing with angry customers, how to handle different personalities, how to be friendly and welcoming no matter the situation, how you find things to do when the store isn't busy and how to handle the stress when it's really busy, promoting teamwork and helping others, etc.

What aspect of civil engineering interests you? I went the typical route of getting a civil engineering degree and now work in construction management. However, I know quite a few people in the industry that had very different routes. If you like the design aspect of engineering, there is a popular software called Navisworks that is being used to model buildings in 3D space. It is also being used to design and coordinate MEP (mechanical, electrical, plumbing) components in buildings. I took a course in college and absolutely loved it. It is super fun and I found it fairly intuitive. If going back to school full time isn't in the cards, you may want to enroll in a course and get certified in Navisworks modeling and then seek out a job with a commercial mechanical or electrical contractor that does their own modeling. This isn't a sure-fire way of breaking into the industry, but I do know people who have taken this path and are incredibly successful. From there, you can decide where you want to go and could always go back to school to become an accredited engineer.