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	$62.78	6.485%	$66.8513	$66.85	$66.85	$66.90
Purchase #2	$128.75	10.516%	$142.2894	$142.29	$142.30	$142.30
Purchase #3	$105.51	5.233%	$111.0313	$111.03	$111.05	$111.00
Purchase #4	$44.50	5.408%	$46.9066	$46.91	$46.90	$46.90
Purchase #5	$157.32	3.504%	$162.8325	$162.83	$162.85	$162.80
Purchase #6	$134.67	13.340%	$152.635	$152.64	$152.65	$152.60
Purchase #7	$134.53	6.441%	$143.1951	$143.20	$143.20	$143.20
7 purchase totals =	$768.06		$825.7412	$825.75	$825.80	$825.70