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	$52.86	13.267%	$59.8729	$59.87	$59.85	$59.90
Purchase #2	$109.53	7.448%	$117.6878	$117.69	$117.70	$117.70
Purchase #3	$240.38	13.413%	$272.6222	$272.62	$272.60	$272.60
Purchase #4	$189.88	5.733%	$200.7658	$200.77	$200.75	$200.80
Purchase #5	$42.36	10.378%	$46.7561	$46.76	$46.75	$46.80
Purchase #6	$18.72	9.287%	$20.4585	$20.46	$20.45	$20.50
Purchase #7	$15.85	10.418%	$17.5013	$17.50	$17.50	$17.50
7 purchase totals =	$669.58		$735.6646	$735.67	$735.60	$735.80