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	$137.56	5.843%	$145.5976	$145.60	$145.60	$145.60
Purchase #2	$244.85	4.257%	$255.2733	$255.27	$255.25	$255.30
Purchase #3	$225.74	11.822%	$252.427	$252.43	$252.45	$252.40
Purchase #4	$98.61	3.323%	$101.8868	$101.89	$101.90	$101.90
Purchase #5	$55.32	13.476%	$62.7749	$62.77	$62.75	$62.80
Purchase #6	$100.75	10.786%	$111.6169	$111.62	$111.60	$111.60
Purchase #7	$221.27	11.811%	$247.4042	$247.40	$247.40	$247.40
7 purchase totals =	$1,084.10		$1,176.9807	$1,176.98	$1,176.95	$1,177.00