LTspice XVII autozooms whenever there is new data to plot. To zoom up on an area, simply drag a box about the region you wish to see drawn larger.
Note that the size of the zoom box is displayed on the status bar at the bottom so that you can quickly measure differences without setting up attached cursors.
There are toolbar buttons and menu commands for zooming out, panning, and returning to the autoranged zoom. The undo and redo commands allow you to review the different zooms used.
Another zoom mode is to hold down the control key while moving the mouse or turning the mouse wheel. The software will zoom and pan a bitmap of the current plot to give an indication of what the plot would like like when fully rendered. This mode is intended for huge waveform files that take seconds to redraw.