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	$54.99	7.780%	$59.2682	$59.27	$59.25	$59.30
Purchase #2	$104.80	8.509%	$113.7174	$113.72	$113.70	$113.70
Purchase #3	$115.65	11.525%	$128.9787	$128.98	$129.00	$129.00
Purchase #4	$213.49	6.864%	$228.144	$228.14	$228.15	$228.10
Purchase #5	$37.34	8.169%	$40.3903	$40.39	$40.40	$40.40
Purchase #6	$229.55	11.522%	$255.9988	$256.00	$256.00	$256.00
Purchase #7	$173.90	10.255%	$191.7334	$191.73	$191.75	$191.70
7 purchase totals =	$929.72		$1,018.2308	$1,018.23	$1,018.25	$1,018.20