I use a very simple spreadsheet to keep my records.
The top half of the "page" is for inventory control where I have the date listed, quantity, item name, supply cost, selling price and shipping charge.
When something sells I copy that entry down to the "sold' section.
For my sales I record the date of sale, what was sold and quantity, cost of supplies, selling price, shipping charge, buyer name, date shipped. I also record the Etsy fees, paypal fees, postage paid and delivery date.
Since each column has a running total I know at a glance what my income is for the month.
I set up the spreadsheet when I first opened my shop and as long as I keep the inventory updated its pretty accurate.
I keep one page for each month.
As far as recording the finances, I keep a simple ledger book (online) that corresponds to my paypal account and a separate page for my business banking account.
For each sale I record what was sold, the paypal fees, and the postage paid.
Since I purchase everything for the business either through paypal or through a credit card, the business leger is very simple to keep accurately.
When it comes to taxes I can simply sum the categories in the ledgers and see exactly what I've spent on everything.
It probably sounds a lot more complicated than it is but it works for me!