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	$140.98	13.772%	$160.3958	$160.40	$160.40	$160.40
Purchase #2	$70.43	8.638%	$76.5137	$76.51	$76.50	$76.50
Purchase #3	$163.65	9.208%	$178.7189	$178.72	$178.70	$178.70
Purchase #4	$79.84	12.419%	$89.7553	$89.76	$89.75	$89.80
Purchase #5	$246.65	6.196%	$261.9324	$261.93	$261.95	$261.90
Purchase #6	$165.31	11.699%	$184.6496	$184.65	$184.65	$184.60
Purchase #7	$232.89	10.301%	$256.88	$256.88	$256.90	$256.90
7 purchase totals =	$1,099.75		$1,208.8457	$1,208.85	$1,208.85	$1,208.80