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	$62.51	11.863%	$69.9256	$69.93	$69.95	$69.90
Purchase #2	$90.85	10.869%	$100.7245	$100.72	$100.70	$100.70
Purchase #3	$103.70	7.285%	$111.2545	$111.25	$111.25	$111.30
Purchase #4	$71.27	9.808%	$78.2602	$78.26	$78.25	$78.30
Purchase #5	$34.77	5.142%	$36.5579	$36.56	$36.55	$36.60
Purchase #6	$160.83	3.790%	$166.9255	$166.93	$166.95	$166.90
Purchase #7	$183.90	11.403%	$204.8701	$204.87	$204.85	$204.90
7 purchase totals =	$707.83		$768.5183	$768.52	$768.50	$768.60