Below is a method to do what I am hoping for, but it is not as elegant as I hoped and involves multiple plots that mimic grid lines
x=[20:0.1:80];
y=sin(x);
plot(x,y,'r','Linewidth',2)
ylim([0 4]);
xlim([0 100]);
% gridlines ---------------------------
hold on
g_y=[0:0.1:4]; % user defined grid Y [start:spaces:end]
g_x=[0:2:100]; % user defined grid X [start:spaces:end]
for i=1:length(g_x)
plot([g_x(i) g_x(i)],[g_y(1) g_y(end)],'k:') %y grid lines
hold on
end
for i=1:length(g_y)
plot([g_x(1) g_x(end)],[g_y(i) g_y(i)],'k:') %x grid lines
hold on
end
print(1,'-dpng','-r300','K1') %save plot as png (looks better)