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	$20.76	7.289%	$22.2732	$22.27	$22.25	$22.30
Purchase #2	$142.89	12.244%	$160.3855	$160.39	$160.40	$160.40
Purchase #3	$57.66	3.194%	$59.5017	$59.50	$59.50	$59.50
Purchase #4	$68.28	9.103%	$74.4955	$74.50	$74.50	$74.50
Purchase #5	$223.90	9.211%	$244.5234	$244.52	$244.50	$244.50
Purchase #6	$167.85	4.344%	$175.1414	$175.14	$175.15	$175.10
Purchase #7	$221.48	5.376%	$233.3868	$233.39	$233.40	$233.40
7 purchase totals =	$902.82		$969.7075	$969.71	$969.70	$969.70