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	$128.76	11.200%	$143.1811	$143.18	$143.20	$143.20
Purchase #2	$231.71	9.558%	$253.8568	$253.86	$253.85	$253.90
Purchase #3	$134.65	4.753%	$141.0499	$141.05	$141.05	$141.00
Purchase #4	$219.39	4.149%	$228.4925	$228.49	$228.50	$228.50
Purchase #5	$49.68	10.481%	$54.887	$54.89	$54.90	$54.90
Purchase #6	$236.78	4.606%	$247.6861	$247.69	$247.70	$247.70
Purchase #7	$98.27	13.139%	$111.1817	$111.18	$111.20	$111.20
7 purchase totals =	$1,099.24		$1,180.3351	$1,180.34	$1,180.40	$1,180.40