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	$145.63	5.639%	$153.8421	$153.84	$153.85	$153.80
Purchase #2	$241.40	6.122%	$256.1785	$256.18	$256.20	$256.20
Purchase #3	$146.82	4.297%	$153.1289	$153.13	$153.15	$153.10
Purchase #4	$190.97	11.272%	$212.4961	$212.50	$212.50	$212.50
Purchase #5	$136.70	8.463%	$148.2689	$148.27	$148.25	$148.30
Purchase #6	$52.50	12.685%	$59.1596	$59.16	$59.15	$59.20
Purchase #7	$237.87	8.773%	$258.7383	$258.74	$258.75	$258.70
7 purchase totals =	$1,151.89		$1,241.8124	$1,241.82	$1,241.85	$1,241.80