Tax not calculated and Checkout keeps refreshing in IE

Hi!

I have reviewed many of the topics related to the checkout refresh issue, but I can’t seem to get it to work despite trying the suggested solutions. The tax calculates correctly and the purchase button works fine in Firefox and Chrome, but neither work in IE. Please help!

http://www.testsite.carroll.org/

Thank you in advance!

https://wordpress.org/plugins/wp-e-commerce/