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	$120.96	10.117%	$133.1975	$133.20	$133.20	$133.20
Purchase #2	$199.55	12.222%	$223.939	$223.94	$223.95	$223.90
Purchase #3	$173.77	4.559%	$181.6922	$181.69	$181.70	$181.70
Purchase #4	$153.37	12.729%	$172.8925	$172.89	$172.90	$172.90
Purchase #5	$213.78	3.826%	$221.9592	$221.96	$221.95	$222.00
Purchase #6	$240.81	6.116%	$255.5379	$255.54	$255.55	$255.50
Purchase #7	$75.88	5.668%	$80.1809	$80.18	$80.20	$80.20
7 purchase totals =	$1,178.12		$1,269.3992	$1,269.40	$1,269.45	$1,269.40