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	$123.68	11.476%	$137.8735	$137.87	$137.85	$137.90
Purchase #2	$195.33	7.332%	$209.6516	$209.65	$209.65	$209.70
Purchase #3	$189.69	5.381%	$199.8972	$199.90	$199.90	$199.90
Purchase #4	$89.45	12.757%	$100.8611	$100.86	$100.85	$100.90
Purchase #5	$86.25	9.536%	$94.4748	$94.47	$94.45	$94.50
Purchase #6	$239.41	5.561%	$252.7236	$252.72	$252.70	$252.70
Purchase #7	$58.72	12.451%	$66.0312	$66.03	$66.05	$66.00
7 purchase totals =	$982.53		$1,061.5130	$1,061.50	$1,061.45	$1,061.60