Those pages are views, so style them as any other view:

1. Go to page when you are logged in as admin, find and click "Edit view" link.

2. On view edit page open "Advanced" view settings and click "Theming information"

3. There you can see how you should name your templates (i.e. views-view--commerce-cart-summary--default.tpl.php) and also if you at template name at beginning of the row (i.e. first is "Display output" you can see default template, copy it, save with other name in your theme's template dir and modify it as you like).

4. Or, you can build those pages (views) on your own. http://www.drupalcommerce.org/user-guide/modifying-shopping-cart-using-views

Cart page is just a view, so style it as any other view:

1. Go to page when you are logged in as admin, find and click "Edit view" link.

2. On view edit page open "Advanced" view settings and click "Theming information"

3. There you can see how you should name your templates (i.e. views-view--commerce-cart-summary--default.tpl.php) and also if you at template name at beginning of the row (i.e. first is "Display output" you can see default template, copy it, save with other name in your theme's template dir and modify it as you like).

4. Or, you can build those pages (views) on your own. http://www.drupalcommerce.org/user-guide/modifying-shopping-cart-using-views