Can you plug a 115V appliance into a 120V outlet?

For residential service 110V, 115V, 117V, 120V, and 125V are all functionally the same. Electric companies have been slowly increasing the line voltage over the last 100 years to cope with increased loads. That is where these different voltages come from.

The tolerance is generally +/-10%. That's +/- 11.5 volts in this case. So, a 115VAC appliance will run between 103.5 and 126.5VAC.

The short answer is yes. 110V appliances can work with up to 130V without being burnt, additionally, 220V appliances can work with up to 240V without being burnt.