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	$195.39	11.296%	$217.4613	$217.46	$217.45	$217.50
Purchase #2	$140.52	13.113%	$158.9464	$158.95	$158.95	$158.90
Purchase #3	$174.72	8.700%	$189.9206	$189.92	$189.90	$189.90
Purchase #4	$15.95	3.196%	$16.4598	$16.46	$16.45	$16.50
Purchase #5	$86.36	13.730%	$98.2172	$98.22	$98.20	$98.20
Purchase #6	$227.72	12.398%	$255.9527	$255.95	$255.95	$256.00
Purchase #7	$105.99	6.514%	$112.8942	$112.89	$112.90	$112.90
7 purchase totals =	$946.65		$1,049.8522	$1,049.85	$1,049.80	$1,049.90