Croket!

From ebookjapan: If you manage to fill a piggy bank full of forbidden gold coins, any wish of yours will be granted. Those called "bankers" travel the world collecting those coins, and fighting to take them from each other. The energetic young boy Croket sets out on a journey as a banker as well, hoping to have his own wish granted! This is a grand adventure-style story, filled with mystery, laughs, and action! Croket! received the 2003 Shogakukan Manga Award for children's manga.