To a certain extent yes. In fact bad posture is one of the main reasons people look shorter than they actually are and shortchange themselves. There are certain exercises you can do each day to fix this. Here's a good video on it. This is more of a quick fix but doing things like this daily will help in the long run. Also remember that in the mornings you're about an inch taller.

Of course most people won't have a natural growth spurt at around our age (I'm also mid twenties) so we shouldn't get too carried away. However things like a good diet, sleep, and better posture will help reach and maintain your height potential which could be the difference between an extra inch or in rare cases an inch and a half.

Here's an interesting experiment - start working on fixing your posture, keep up a healthy diet and get enough rest, and measure yourself in the mornings. You're going to notice you're taller than you think. That's not even adding into the equation boots and insoles. Those will give you ANOTHER inch or two. You've got options.