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	$163.74	12.749%	$184.6152	$184.62	$184.60	$184.60
Purchase #2	$114.43	12.700%	$128.9626	$128.96	$128.95	$129.00
Purchase #3	$10.49	6.829%	$11.2064	$11.21	$11.20	$11.20
Purchase #4	$54.98	8.368%	$59.5807	$59.58	$59.60	$59.60
Purchase #5	$190.48	4.855%	$199.7278	$199.73	$199.75	$199.70
Purchase #6	$104.43	13.580%	$118.6116	$118.61	$118.60	$118.60
Purchase #7	$224.64	6.342%	$238.8867	$238.89	$238.90	$238.90
7 purchase totals =	$863.19		$941.5910	$941.60	$941.60	$941.60