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	$172.59	3.158%	$178.0404	$178.04	$178.05	$178.00
Purchase #2	$143.82	6.747%	$153.5235	$153.52	$153.50	$153.50
Purchase #3	$49.45	7.387%	$53.1029	$53.10	$53.10	$53.10
Purchase #4	$37.33	12.102%	$41.8477	$41.85	$41.85	$41.80
Purchase #5	$244.70	4.444%	$255.5745	$255.57	$255.55	$255.60
Purchase #6	$198.90	11.837%	$222.4438	$222.44	$222.45	$222.40
Purchase #7	$59.71	3.430%	$61.7581	$61.76	$61.75	$61.80
7 purchase totals =	$906.50		$966.2909	$966.28	$966.25	$966.20