Most consumers notice the first digit when it comes to shopping.
For example: If you were to look at a bag of candy for 5$, surely you'd think "wow, for only (said amount) of servings, this is pretty expensive." Now I understand that not everyone grabs a bag of candy and looks for serving sizes. However, maybe if you saw a bag of candy for $4.99 and it said "HALLOWEEN SALE!" which first two things would you see first? A majority of shoppers will notice the "4" and "SALE!" before anything else, most grabbing that bag of deliciousness without considering penny-cent taxes and etc. This goes for so many other situations.
Another example is ads on tv you might see. Personally, I've noticed that mattress companies are practically one of the four muskateers: they usually say things such as "This mattress was $500 but now its on sale for $499!" or something like that. Once again, because the shopper sees "Was", "sale", and "4" one would instantly think "Oh wow! A great deal!"
Also, keep in mind companies do not always use the "99" cent pricing. Sometimes they use 98 or even 95. Always keep in mind that at the end of the day it all comes down to 5$ (in this case to your question, 100) with possible taxes depending on what you're getting.
I hope my answer was helpful. :)
