I'm building an LED driver from a ST reference design. However, one of the shunt resistors called for is 226 mOhms and digikey doesn't have any 226mOhm shunt resistors. I've found 220mOhm and a 5mOhm that I could put in series and measure across both bot not sure if I can just go with the 220mOhm alone or how important it is to get close or have the exact value.

 

You don't need to be with in 1%, or even 5%.
226m=220 (almost)

LED current is measured at Rvfb. The current measured at Rsns is (more or less) the input current and not very related to LED current.