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	$173.81	13.246%	$196.8329	$196.83	$196.85	$196.80
Purchase #2	$19.83	7.163%	$21.2504	$21.25	$21.25	$21.30
Purchase #3	$22.90	5.785%	$24.2248	$24.22	$24.20	$24.20
Purchase #4	$69.57	11.645%	$77.6714	$77.67	$77.65	$77.70
Purchase #5	$114.83	4.290%	$119.7562	$119.76	$119.75	$119.80
Purchase #6	$171.28	12.696%	$193.0257	$193.03	$193.05	$193.00
Purchase #7	$201.50	10.515%	$222.6877	$222.69	$222.70	$222.70
7 purchase totals =	$773.72		$855.4491	$855.45	$855.45	$855.50