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	$94.70	11.772%	$105.8481	$105.85	$105.85	$105.80
Purchase #2	$118.40	13.405%	$134.2715	$134.27	$134.25	$134.30
Purchase #3	$162.65	5.868%	$172.1943	$172.19	$172.20	$172.20
Purchase #4	$25.65	6.796%	$27.3932	$27.39	$27.40	$27.40
Purchase #5	$110.60	5.390%	$116.5613	$116.56	$116.55	$116.60
Purchase #6	$99.40	5.103%	$104.4724	$104.47	$104.45	$104.50
Purchase #7	$245.74	4.115%	$255.8522	$255.85	$255.85	$255.90
7 purchase totals =	$857.14		$916.5930	$916.58	$916.55	$916.70