My customer wants to charge a 2% shipping insurance cost if the user selects credit card as Payment method is there a way to add tis cost in Expresso Store?
There is nothing out of the box that would allow you to do this. The best option would be to build an extension that uses one of store_order_recalculate hook to add the percentage to the order.
The other option would be to modify the payment gateway in question to add the 2%. If the gateway is one of the default you will need to reapply this each time you update Store.
You could create a "tax" for it, that applies to any country and region, and call it "Shipping Insurance". That seems to be the most straight way, but of course it would be applied to all payment methods.
View docs here