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	$76.45	9.514%	$83.7235	$83.72	$83.70	$83.70
Purchase #2	$160.73	7.278%	$172.4279	$172.43	$172.45	$172.40
Purchase #3	$115.27	9.734%	$126.4904	$126.49	$126.50	$126.50
Purchase #4	$86.25	9.311%	$94.2807	$94.28	$94.30	$94.30
Purchase #5	$89.94	13.290%	$101.893	$101.89	$101.90	$101.90
Purchase #6	$149.86	5.249%	$157.7262	$157.73	$157.75	$157.70
Purchase #7	$152.26	4.130%	$158.5483	$158.55	$158.55	$158.50
7 purchase totals =	$830.76		$895.0900	$895.09	$895.15	$895.00