Why the interviewer is asking this question: The interviewer is asking to align expectations for the role with your long-term expectations. While interviewers typically want solid alignment on near term (i.e. under 5 years) expectations, more latitude can and will be given for longer term goals.
If they don't want to give benefits to stocker and cashiers they should have part time hours and paid $17.50 per hour no benefits. Also how many teenagers would like a parttime job from 3 pm until 7pm and maybe get the pay they give their cashiers $8 -9 an hour.
We will need to know that before we can answer your question. There are some people who can save $10,000 in a year and be making only $20,000 a year. There are some who make $1,000,000 a year and will never be able to save $5000. It all boils down to how much money you have leftover after you pay the bills.