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	$54.71	10.692%	$60.5596	$60.56	$60.55	$60.60
Purchase #2	$116.81	12.533%	$131.4498	$131.45	$131.45	$131.40
Purchase #3	$161.31	10.604%	$178.4153	$178.42	$178.40	$178.40
Purchase #4	$70.40	8.569%	$76.4326	$76.43	$76.45	$76.40
Purchase #5	$56.56	9.528%	$61.949	$61.95	$61.95	$61.90
Purchase #6	$233.36	12.599%	$262.761	$262.76	$262.75	$262.80
Purchase #7	$28.42	5.300%	$29.9263	$29.93	$29.95	$29.90
7 purchase totals =	$721.57		$801.4936	$801.50	$801.50	$801.40