Argthtjtr

I will be travelling to the US and have some (clarification: 7 or 8) 100 USD banknotes. When I arrive there, I would like to change them into 5/10/20 USD banknotes, to use when credit cards are impractical (probably mostly tips or small purchases).

Is it acceptable / customary / expected / normal to walk into a random bank office and ask for such change? Is there a fee for the change?

Any other options?

Is it acceptable / customary / expected / normal to walk into a random bank office and ask for such change? Is there a fee for the change?

It is acceptable. Some banks may be more accommodating than others. I would expect smaller banks and those that emphasize customer service to be among the former. Larger commercial banks are more likely to be among the latter. There should be no fee.

Any other options?

Make small purchases, one for each $100 note. To be courteous, tell the cashier that you have no smaller banknotes before you present the merchandise, to give an opportunity to decline the transaction if the store lacks sufficient small change. Many stores refuse to accept $100 bills altogether, so you may have to try a few places before you'll find one that will accommodate you.

In practice, people commonly pay with $20 notes, so most stores will have a large number of these on hand. Making a $5 purchase with a $100 note isn't likely to cause more inconvenience than making the same purchase with a $20 note.

If you're staying at a hotel, you could ask at the front desk. Cash is still common enough in the USA that I would expect that most hotels would have enough cash on hand to accommodate you.

While I would be surprised if a "nice" hotel were unable to do this, I should say that I have never actually tried it myself.

It is common for retailers to provide change (we call this "breaking a bill".) Almost any major chain retailer will break a $100 for a small transaction. You may get attitude though because places like Wal-Mart may have to get extra manager approval to accept the bill or test it using a chemical ink to ensure it is not counterfeit but they will usually do it anyway after hassling you. A smaller business like a gas/petrol station may entirely refuse to accept the bill. Breaking a $100 bill is almost always possible but almost always a hassle.

Since you're asking this, you may also be interested in knowing:

Getting/using coins is not always easy but may be necessary. Many coin operated machines in the US accept quarters only. If you find yourself needing quarters ($0.25) you can usually get them in laundromats from a change machine in exchange for $1 or $5 bills. I run into this all the time when trying to pay for parking. Also, retailers have the right to refuse to accept payment in "burdensome" quantities of small coins. No, you should not pay for a cheeseburger with 600 pennies. In fact, many places will only accept coins if you are paying in exact change. People hate pennies. They are damaging our economy, it costs 2.5 cents to make a 1 cent penny. We only manufacture them still because of Zinc lobbyists and Lincoln fans.

Apple/Google Pay are quickly becoming widely accepted as forms of payment but you should always ask before accepting a service.

In the US, you will often be offered services before you pay. This confuses many tourist who end up getting in trouble once they have consumed a product or service not realizing their method of payment will not be accepted. An example is ordering street food without realizing they are expecting cash only. You probably won't get into any serious trouble but you'll likely get harassed or belittled.