Shopping carts on online marketplaces matter a lot. If it looks poor, people will generally avoid it. I personally like the design by Amazon and their shopping cart. It looks trustworthy for the most part. Here's what I think is crucial in shopping cart softwares:
- The ability to add to your cart. You may want to continue shopping, and if there's a limit to only one per cart, that would be abusrd.
- The ability to check off what want to buy. Say there are 4 items in your cart. You only want to buy 2. You can tick the two you want, or have an option to save the other two for the future.
- Adding promo codes. Sometimes, there are promo codes, and if there's no option to add that, it would be a shame.
- Last but not least, the payment options. If there's only a payment option and noone has ever heard of it, chances are, the buyer will leave.