It entirely depends on the specifications that are asked of you. If you are doing an independent project from home, then accent shouldn't be a problem at all. That said, a lot of audition requests that get posted give a description of the voice they are looking for. For example:
"Fleet Commander Jacobs - Male, age 25 to 35 - Australian accent - A gravelly deep voice with a sense of authority, very stern."
If they ask for something specific like that, then you can either give it your best attempt and work on the accent or look elsewhere. The people who are looking for voice actors can also be lenient and decide to change the characters accent just to fit your own because they really like your voice, regardless of the accent. So don't feel put off from auditioning just because they asked for a specific accent, unless they state with 100% conviction that the particular character MUST have a specific accent.
That being said, having the ability to mimic different accents is a major bonus, not to blow my own trumpet but I would know
. Plus having a variety of accents to choose from can help you to diversify your work more and garner more interest towards people who want to work with you. So just give a few accents a practice and over time, you will eventually sound like a natural.