[Revised Nov 2015].
Design Considerations
After discussion with many pharmacies who had tried different methods, it became apparent that there is no rounding method that is acceptable to all customers.
Swedish rounding has been tried... that is all items priced to 1c, and the grand total rounded where 28c, 29c, 31c and 32c all go to 30c, whereas 33c, 34c, 36c, 37c all go to 35c. This caused a surprising amount of disagreement from customers, some of who stormed out vowing never to return when $3.28 was rounded to $3.30.
So, instead the program rounds at item level, thus an item whose raw retail works out at $3.57 is rounded to a retail of $3.60. There is therefore no problem since a price of $3.57 cannot appear on the sale since it is stored at $3.60. What the customer sees is what they pay. Of course, this makes it impossible to have the item displayed at $3.99, it has to be either $3.95 or $4.00. However, what is lost on some items where the decision is made to round down is more than gained back from those where it rounds up…. $3.57 to $3.60.
There will be users who will feel passionately that it should price to 1c and use Swedish rounding. There will be others who will be equally passionate for item-level rounding so that you avoid all the arguments. Both sides (and there will be others) will not only know what they want but also be sure that all 'Right thinking' people would feel the same and that anything else is wrong (and probably illegal and immoral as well).
There is no right answer on this… in one way the problem is that of having a debased currency whose smallest currency unit does not have a coin. But on the other hand, even when 1c coins existed the problem still existed in that a price could come out to $3.575 which was rounded to $3.58 because there was no 1/2c coin. Now there is no coin less than 5c, so by the same reasoning one rounds the unit retail price to the size of the smallest coin, thereby avoiding arguments.
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