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	$196.91	10.471%	$217.5284	$217.53	$217.55	$217.50
Purchase #2	$232.58	13.281%	$263.4689	$263.47	$263.45	$263.50
Purchase #3	$94.62	11.377%	$105.3849	$105.38	$105.40	$105.40
Purchase #4	$131.53	9.154%	$143.5703	$143.57	$143.55	$143.60
Purchase #5	$66.27	12.805%	$74.7559	$74.76	$74.75	$74.80
Purchase #6	$248.52	12.109%	$278.6133	$278.61	$278.60	$278.60
Purchase #7	$130.48	6.748%	$139.2848	$139.28	$139.30	$139.30
7 purchase totals =	$1,100.91		$1,222.6065	$1,222.60	$1,222.60	$1,222.70