It depends on some factors. First of them is: Is
piggybank.com in the same branch as you are? If it is clearly something completely different, it might turn into a problem.
Then, is your name (now
piggybank) some general word? Like Apple (Those lawyers have pulled some magic). If it is something less broad, something specific, that will increase your odds.
The age of that website is important, as well as the contents. Is it a blank 'this domain is still free' page, or is it an active website? If it is blank, it'll increase the chances you can get it.
I suggest that you register the name, and use that proof to contact the current owner of
piggybank.com. Instead of draging this through some legal process, you can offer some reasonable amount.
It will save you some few hundreds in legal-fees, and the same goes for them.
You can contact ICANN about this and ask what the requirement are for them to 'take over' the domain and give it to you, but they'll try to stay away from this type of problems as much as they can, this always gets messy when it goes wrong.