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	$105.65	6.594%	$112.6166	$112.62	$112.60	$112.60
Purchase #2	$94.95	6.167%	$100.8056	$100.81	$100.80	$100.80
Purchase #3	$95.27	10.391%	$105.1695	$105.17	$105.15	$105.20
Purchase #4	$18.77	4.401%	$19.5961	$19.60	$19.60	$19.60
Purchase #5	$76.85	12.235%	$86.2526	$86.25	$86.25	$86.30
Purchase #6	$205.76	12.851%	$232.2022	$232.20	$232.20	$232.20
Purchase #7	$241.40	10.130%	$265.8538	$265.85	$265.85	$265.90
7 purchase totals =	$838.65		$922.4964	$922.50	$922.45	$922.60