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	$8.95	11.683%	$9.9956	$10.00	$10.00	$10.00
Purchase #2	$216.89	7.457%	$233.0635	$233.06	$233.05	$233.10
Purchase #3	$196.66	11.136%	$218.5601	$218.56	$218.55	$218.60
Purchase #4	$190.80	4.731%	$199.8267	$199.83	$199.85	$199.80
Purchase #5	$58.92	13.408%	$66.82	$66.82	$66.80	$66.80
Purchase #6	$76.42	11.564%	$85.2572	$85.26	$85.25	$85.30
Purchase #7	$78.62	8.286%	$85.1345	$85.13	$85.15	$85.10
7 purchase totals =	$827.26		$898.6576	$898.66	$898.65	$898.70