Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$12.61	11.582%	$14.0705	$14.07	$14.05	$14.10
Purchase #2	$211.29	7.664%	$227.4833	$227.48	$227.50	$227.50
Purchase #3	$54.46	3.706%	$56.4783	$56.48	$56.50	$56.50
Purchase #4	$73.57	11.391%	$81.9504	$81.95	$81.95	$82.00
Purchase #5	$217.82	10.404%	$240.482	$240.48	$240.50	$240.50
Purchase #6	$59.54	5.116%	$62.5861	$62.59	$62.60	$62.60
Purchase #7	$126.35	6.792%	$134.9317	$134.93	$134.95	$134.90
7 purchase totals =	$755.64		$817.9823	$817.98	$818.05	$818.10