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	$126.74	13.529%	$143.8867	$143.89	$143.90	$143.90
Purchase #2	$129.74	9.206%	$141.6839	$141.68	$141.70	$141.70
Purchase #3	$158.33	8.745%	$172.176	$172.18	$172.20	$172.20
Purchase #4	$95.61	7.794%	$103.0618	$103.06	$103.05	$103.10
Purchase #5	$80.25	13.165%	$90.8149	$90.81	$90.80	$90.80
Purchase #6	$45.51	5.730%	$48.1177	$48.12	$48.10	$48.10
Purchase #7	$22.99	6.670%	$24.5234	$24.52	$24.50	$24.50
7 purchase totals =	$659.17		$724.2644	$724.26	$724.25	$724.30