Kilimanjaro Currency, the main currency (Tsh). USD is widely accepted in tourist areas however older notes US dollars printed prior to 2001 are not accepted anywhere in Tanzania or many other African countries.
Changing money in Tanzania is not a problem in most populated areas. Hotels usually have a worse rate than banks, so you should go to a Forex office (aka Bureau de Change) or bank if possible. You may have to wait in line for a bit. Banks in Tanzania are just like banks in the US or the UK. The main banks include NBC, CRDB, Exim Bank, Barclays Bank and Standard Chartered. It should be noted the bank exchange rates are almost always substantially worse than those at a Forex. Kilimanjaro Currency
ATMs (cash points) are located in almost all banks with 24-hour access and give the same exchange rate as the bank. They may require a Visa card. Inquire if there is any additional fee for withdrawing using a Visa debit card.
When leaving the country, you need to exchange Tanzania shillings back for USD or other foreign currency before you leave Tanzania. The Forex office (aka Bureau de Change) has the best Tsh to USD rate. There are one or more Forex offices in each international airport. You can also find them in most cities.