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	$221.94	6.797%	$237.0253	$237.03	$237.05	$237.00
Purchase #2	$111.40	10.478%	$123.0725	$123.07	$123.05	$123.10
Purchase #3	$250.27	5.321%	$263.5869	$263.59	$263.60	$263.60
Purchase #4	$65.98	11.235%	$73.3929	$73.39	$73.40	$73.40
Purchase #5	$91.60	9.298%	$100.117	$100.12	$100.10	$100.10
Purchase #6	$16.89	8.635%	$18.3485	$18.35	$18.35	$18.30
Purchase #7	$95.35	5.538%	$100.6305	$100.63	$100.65	$100.60
7 purchase totals =	$853.43		$916.1736	$916.18	$916.20	$916.10