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	$141.45	13.616%	$160.7098	$160.71	$160.70	$160.70
Purchase #2	$208.85	6.755%	$222.9578	$222.96	$222.95	$223.00
Purchase #3	$68.79	5.309%	$72.4421	$72.44	$72.45	$72.40
Purchase #4	$136.36	10.115%	$150.1528	$150.15	$150.15	$150.20
Purchase #5	$200.54	10.422%	$221.4403	$221.44	$221.45	$221.40
Purchase #6	$151.38	6.792%	$161.6617	$161.66	$161.65	$161.70
Purchase #7	$177.78	3.272%	$183.597	$183.60	$183.60	$183.60
7 purchase totals =	$1,085.15		$1,172.9615	$1,172.96	$1,172.95	$1,173.00