Get pretty close approximation (so to speak :) ) that way...
hAx=axes;
xlim([0,27])
set(hAx,'xtick',[0 15 25])
hT=text(7.5, 0.0, '\approx', ...
'fontsize',14,'fontweight','bold', ...
'rotation',90,'horizontalalign','center');
produces
You'll have to rig up the actual axis limits it you want the asymmetrical ticks vis a vis position. Depending on what you actually have, may be able to just use 'xticklabel' with appropriate values at existing tick locations.
