Shopping cart

I’m fairly new to WordPress and am using templates from Studiopress (previously Revolution). I’ve set up a new site for the Arran Folk Festival (http://wordpress.arranfolkfestival.com/). One of the requirements is the setting up of a shopping cart for the sale of e-tickets for concerts and merchandise. Is there a recommended plug-in that would be reliable and secure? We’re happy to pay for such a service, as long as it’s reliable and can do what we need it to do.

Many thanks
Camuel