Even if your retail store sells only to cash customers, you'll need somewhere other than a sock to store your cash. Add to this the complexities of personal checks, traveler's checks, credit cards, and debit cards, and you have even more need for a bank.
A bank is a commercial or state institution that provides various financial services. Most banks take deposits, make loans, and offer related financial products. Business banks specialize in the needs of businesses rather than consumers. A small retail store doesn't require a business bank to handle its financial account unless large amounts of cash and credit are involved. If possible, set up a small business account at your current bank or credit union. Most financial institutions usually will be more responsive to existing customers. If you plan to do much of your banking online, make sure the bank you select has capability for it.
When setting up a business account, you will need documents that show you have filed for a fictitious business name (DBA) and that you are its owner. In addition, you will need an address, preferably of your store, but it could be a post office box or temporary address. You also will need personal identification, which is an easier task if you already have an account at the bank.
At the time you open your account, ask about other financial services the bank offers to small businesses. You may want to use them someday. In addition, find out how to prepare deposits and deliver them to the bank. Most banks have a night deposit box where you can leave one of their deposit bags anytime, day or night. If you've not done a business deposit before, ask your banker or a teller for assistance.