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	$213.62	13.208%	$241.8349	$241.83	$241.85	$241.80
Purchase #2	$145.62	5.393%	$153.4733	$153.47	$153.45	$153.50
Purchase #3	$95.36	4.313%	$99.4729	$99.47	$99.45	$99.50
Purchase #4	$23.50	5.146%	$24.7093	$24.71	$24.70	$24.70
Purchase #5	$11.27	7.727%	$12.1408	$12.14	$12.15	$12.10
Purchase #6	$7.37	3.269%	$7.6109	$7.61	$7.60	$7.60
Purchase #7	$210.88	6.182%	$223.9166	$223.92	$223.90	$223.90
7 purchase totals =	$707.62		$763.1587	$763.15	$763.10	$763.10