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	$170.70	12.393%	$191.8549	$191.85	$191.85	$191.90
Purchase #2	$140.60	7.733%	$151.4726	$151.47	$151.45	$151.50
Purchase #3	$153.72	3.283%	$158.7666	$158.77	$158.75	$158.80
Purchase #4	$49.76	6.596%	$53.0422	$53.04	$53.05	$53.00
Purchase #5	$130.39	10.277%	$143.7902	$143.79	$143.80	$143.80
Purchase #6	$249.78	5.280%	$262.9684	$262.97	$262.95	$263.00
Purchase #7	$233.94	13.762%	$266.1348	$266.13	$266.15	$266.10
7 purchase totals =	$1,128.89		$1,228.0297	$1,228.02	$1,228.00	$1,228.10