generally strike prices are every 5 dollars. under 10 or 20, they allow 2.5 dollar increments. this is for stocks. there have been various pilot programs over the years that have increased the number of strikes. i'm not sure if all stock options trade in pennies yet, but that was also rolled out as a pilot program that keeps getting extended.
regarding the marks, i'm not sure what data you are looking at. the closing mark shouldn't be outside of the bid/ask. the b/a may be extra wide on the close tho.