Example: I have $\pu{64 cm^{3}}$ of milk. How much is that in gallons?
When I use the conversion factors $\frac{\pu{1 mL}}{\pu{1 cm^3}}$ $\frac{\pu{1L}}{\pu{1000 mL}}$ $\frac{\pu{1.0567 qt}}{\pu{1 L}}$ $\frac{\pu{1 gal}}{\pu{4 qt}}$.
I know the final answer should only have two significant figures, but how many significant figures should the intermediate conversion factors have?
I have heard that:
conversion factors should have one more sig fig than the least precise measurement. (So three in this case)
But I also heard that we shouldn't round anything until the end. (So use all 5, and round after conversions are complete)
The reason why I got confused is because of my textbook: