about fifteen years ago the cent
was taken out of circulation, but prices ending on .99 stayed. When you purchase more than one item the total is rounded up or down.
So buying one package of chewinggum
for 0.99 gulden
you pay 1 gulden but three of the same packages together cost 2,97 which is rounded down and sets you back 2,95.
It's really weird when you start thinking about it. But in the long run you pay nothing more or nothing less.
But since the introduction of the Euro this weird phenomenon has gone...