Accounting and bookkeeping are needed for all types of businesses, even dropshipping businesses. Online bookkeeping can help you keep track of your expenses and transactions while you focus your time and energy on which products to sell and on which channels to market your products.
In terms of software, it depends on your preference on how much automation you want to see in your accounting tasks. There is some software that can help you track revenue & profitability across your business while some software helps you read your transactions and categorizes them for you.