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	$93.30	11.136%	$103.6899	$103.69	$103.70	$103.70
Purchase #2	$147.35	10.293%	$162.5167	$162.52	$162.50	$162.50
Purchase #3	$126.79	4.598%	$132.6198	$132.62	$132.60	$132.60
Purchase #4	$143.46	9.774%	$157.4818	$157.48	$157.50	$157.50
Purchase #5	$105.56	10.369%	$116.5055	$116.51	$116.50	$116.50
Purchase #6	$193.52	3.345%	$199.9932	$199.99	$200.00	$200.00
Purchase #7	$22.83	8.834%	$24.8468	$24.85	$24.85	$24.80
7 purchase totals =	$832.81		$897.6537	$897.66	$897.65	$897.60