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	$123.51	11.463%	$137.668	$137.67	$137.65	$137.70
Purchase #2	$205.46	12.795%	$231.7486	$231.75	$231.75	$231.70
Purchase #3	$229.57	11.327%	$255.5734	$255.57	$255.55	$255.60
Purchase #4	$159.66	7.563%	$171.7351	$171.74	$171.75	$171.70
Purchase #5	$62.27	7.509%	$66.9459	$66.95	$66.95	$66.90
Purchase #6	$121.76	5.862%	$128.8976	$128.90	$128.90	$128.90
Purchase #7	$170.38	10.430%	$188.1506	$188.15	$188.15	$188.20
7 purchase totals =	$1,072.61		$1,180.7192	$1,180.73	$1,180.70	$1,180.70