First off, unless you know the local traffic warden, always put money in the meter if there's one there.
The parking fine is bugger all, the real pain is attempting to pay the sodding thing.
If you're unlucky enough to get a ticket you'll need to pay it at the Nadi City Council building, funnily enough its based in Nadi Town. Even if the parking ticket was issued by the LTA, do not go to the LTA in Martintar.
Location of Nadi City Council: If you're coming in from the Denarau Roundabout, drive down the High Street and its in a shopping mall opposite Westpac. When you're in the mall, ask someone to point out the office. If you can't find the mall, if you're near Westpac, a shop owner will know.