For example, our HR app (which is built on Bootstrap + jQuery) has a button for 'Add Employee' on the main employee list, but we have also linked the '+' hotkey to that button so the user does not have to revert to the mouse to add the next employee when doing batch entry.
Within that, there are plenty of grid style entry plugins (mentioned elsewhere in this thread) that you can add on to do things like the invoice screen etc.
But be aware - study the depth of some of these plugins. Invoice entry screens are fraught with all sorts of things like real time validation (e.g. will you allow a user to specify a quantity of an item greater than what is in stock? Can you calculate tax amounts on the fly line by line? Can the user change the pricing of the item on the fly and are there rules that have to be adhered to in order to prevent fraud) etc.
Yes, I've developed invoicing type apps many times before. It certainly has some 'gotchas' that can trip you up, and the UI is certainly a lot more complex that it first appears as you have to adhere to strict accounting principles in the back end.