Rachael, I "oversell" myself all the time. Shop work was the best one: one job, I had keys for as they didn't employ more than 1 staff member at a time and I had to cash up my own till and sometimes a new person would be working with me to "see how it was done."

This morphed into a supervisory role wherein I had responsiblilty for the security of the store in the mornings and evenings when I worked, I cashed up (for many jobs, that's manager-only) and I supervised and trained new people (as well as working the till, doing the sell-by dates, cleaning up...). Don't add that everyone did that too, just tell them that's what you did, above and beyond what, for example, a supermarket would ask a cashier to do (and I did this job as a teenager, well OK age 19, showing how trustworthy I am!).

Let me know what job you're going for and where you think you don't have enough experience, telling me what you do have, and I'll hype it up a bit for you! It's not lying at all, nor is it faking, it's just realising you can do the job and you've done it unofficially for years.