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	$172.91	11.452%	$192.7117	$192.71	$192.70	$192.70
Purchase #2	$205.99	12.474%	$231.6852	$231.69	$231.70	$231.70
Purchase #3	$167.25	13.527%	$189.8739	$189.87	$189.85	$189.90
Purchase #4	$130.75	7.822%	$140.9773	$140.98	$141.00	$141.00
Purchase #5	$103.35	8.162%	$111.7854	$111.79	$111.80	$111.80
Purchase #6	$54.72	12.795%	$61.7214	$61.72	$61.70	$61.70
Purchase #7	$240.45	6.824%	$256.8583	$256.86	$256.85	$256.90
7 purchase totals =	$1,075.42		$1,185.6132	$1,185.62	$1,185.60	$1,185.70