Late Fees for short payment less than $1

It seems that AT&T charges you a $5 late fee when your bill was paid on time but short only .26 cents (due only due for a change in a tax charge).  This is crazy.  When I called to ask about it they eventually credited my account but told me it is system generated and will charge you a late fee if you are short one penny??  I appreciate the need for late fees but there are usually very easy settings in the billing system that can be set for fees only charged if the payment is short greater than $1, $3 or $5 etc.  When you are standard bill charges don't change I don't know how the taxes change but people who automatic payments set up will not notice a 26 cent change in their bill.