It may seem like a small, insignificant detail, but to shoppers, minicarts on ecommerce sites make the shopping experience so much more pleasant and easy. Rather than having to leave the shopping experience to see what is in their full cart, they can easily (usually by simply mousing over a cart icon) see what they have added without leaving the page they are on.
Will the lack of a minicart keep you from getting any sales? No. But it could cause some customers to go to another site where the experience is more seamless.
But of course, it’s not just about having a minicart but making sure it is as useful as possible. These action points will help you do that.