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	$217.75	7.177%	$233.3779	$233.38	$233.40	$233.40
Purchase #2	$240.80	10.559%	$266.2261	$266.23	$266.25	$266.20
Purchase #3	$244.94	5.618%	$258.7007	$258.70	$258.70	$258.70
Purchase #4	$29.85	13.455%	$33.8663	$33.87	$33.85	$33.90
Purchase #5	$144.55	6.271%	$153.6147	$153.61	$153.60	$153.60
Purchase #6	$105.63	5.739%	$111.6921	$111.69	$111.70	$111.70
Purchase #7	$126.48	4.465%	$132.1273	$132.13	$132.15	$132.10
7 purchase totals =	$1,110.00		$1,189.6051	$1,189.61	$1,189.65	$1,189.60