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	$196.58	11.361%	$218.9135	$218.91	$218.90	$218.90
Purchase #2	$16.36	6.545%	$17.4308	$17.43	$17.45	$17.40
Purchase #3	$130.53	3.123%	$134.6065	$134.61	$134.60	$134.60
Purchase #4	$168.62	10.232%	$185.8732	$185.87	$185.85	$185.90
Purchase #5	$105.75	13.210%	$119.7196	$119.72	$119.70	$119.70
Purchase #6	$234.77	7.370%	$252.0725	$252.07	$252.05	$252.10
Purchase #7	$160.58	7.280%	$172.2702	$172.27	$172.25	$172.30
7 purchase totals =	$1,013.19		$1,100.8863	$1,100.88	$1,100.80	$1,100.90