When applying for a job, both in the CV and in the cover letter:

Do:

• Always include additional skills where you know those skills are directly relevant to the job.

Make sure you can show on your CV how those skills were applied. In the shop assistant example, you could include stocktaking, bank reconciliations, balances, and handling cash. The relevance is based on how the job relates to the organization. You're telling them you can do the more complex work.

Don't:

• Don't ever simply apply for any job just showing you have the basic skills and nothing else.
• Don't assume average is good enough when going for a job. It isn't, and never will be. Your cover letter and your application and CV should be interesting and worth looking at, not just another application. The better your application is, the better you'll do. You're trying to get a job, not put people to sleep.