Sorry if the title is wordy. Basically, what I am asking would probably be easier if I just use an example.
Say I wanted to plot $f(x) = A\sin(x)$ and have the graph come up showing the sine function with the ticks on the $y$-axis being half-integer multiples of $A$. What I have been doing for my homework assignments is just plotting $f(x)=\sin(x)$ and then turning off the ticks and manually adding my own ticks. It would be really cool if Mathematica could do this for me.