See documentation how to built e-commerce web site with help of Phoca Cart, Gantry 5 and Joomla!:
Demo
E-commerce demo (Joomla! 3)
Extension demo (Joomla! 3)
Extension demo (Joomla! 2.5)
Extension demo (Joomla! 1.5)
Templates demo (Joomla! 1.5)