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	$109.45	9.577%	$119.932	$119.93	$119.95	$119.90
Purchase #2	$178.27	10.379%	$196.7726	$196.77	$196.75	$196.80
Purchase #3	$145.58	10.707%	$161.1673	$161.17	$161.15	$161.20
Purchase #4	$228.54	9.172%	$249.5017	$249.50	$249.50	$249.50
Purchase #5	$217.78	13.141%	$246.3985	$246.40	$246.40	$246.40
Purchase #6	$52.85	13.197%	$59.8246	$59.82	$59.80	$59.80
Purchase #7	$99.50	3.689%	$103.1706	$103.17	$103.15	$103.20
7 purchase totals =	$1,031.97		$1,136.7673	$1,136.76	$1,136.70	$1,136.80