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	$52.41	4.322%	$54.6752	$54.68	$54.70	$54.70
Purchase #2	$62.72	6.598%	$66.8583	$66.86	$66.85	$66.90
Purchase #3	$146.42	10.248%	$161.4251	$161.43	$161.45	$161.40
Purchase #4	$14.52	13.624%	$16.4982	$16.50	$16.50	$16.50
Purchase #5	$6.85	9.769%	$7.5192	$7.52	$7.50	$7.50
Purchase #6	$101.83	10.802%	$112.8297	$112.83	$112.85	$112.80
Purchase #7	$60.52	4.275%	$63.1072	$63.11	$63.10	$63.10
7 purchase totals =	$445.27		$482.9129	$482.93	$482.95	$482.90