Seems that you have pretty mess in your current packages and available repositories. You seem to have installed various mysql packages from all these repositories: Centos, art, Percona. Also you seems to have Percona-Server-shared-56 already installed, while you cannot mix 5.5 and 5.6 packages.
Try to uninstall all the existing MySQL and Percona Server packages first, and then re-try installing Percona Server 5.5.