Even before getting to the main point, bringing that money into USA as a traveler / visitor will be a hurdle as a threshold exceeding $10,000 must be declared upon entry. Will they allow the entire 5000 OMR stack in or would that be confiscated even when declared?
Like this: after paying for the food in $, suddenly giving them more money: I’m only a visitor (as I only have foreign currency, i.e. Omani Rial in cash) being like, “Here is 5000 OMR ($13,020) for your efforts” so despite that being a lot of money, will they take it?


If you’re giving out money, the server will take it.
If they don’t understand what OMR is, and nobody in the US does, they will have no idea how much you gave them. They don’t know if you made them rich or insulted them. So, don’t expect an appropriate reaction, and don’t expect anyone to be able to give you change.
Some people enjoy holding on to foreign currency, and if you threw in a small OMR bill with the rest of the money in US$, they might just keep it as a collectible and never exchange it at all.
Overall, I would avoid paying in ANY foreign currency in the US. Most vendors will refuse it.
The highest denomination is 50 OMR ($130).
Yeah, I don’t know anyone who would know what to do with that.