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	$95.53	12.562%	$107.5305	$107.53	$107.55	$107.50
Purchase #2	$172.89	3.171%	$178.3723	$178.37	$178.35	$178.40
Purchase #3	$123.67	13.412%	$140.2566	$140.26	$140.25	$140.30
Purchase #4	$142.36	6.307%	$151.3386	$151.34	$151.35	$151.30
Purchase #5	$171.53	3.698%	$177.8732	$177.87	$177.85	$177.90
Purchase #6	$247.53	13.408%	$280.7188	$280.72	$280.70	$280.70
Purchase #7	$55.51	10.605%	$61.3968	$61.40	$61.40	$61.40
7 purchase totals =	$1,009.02		$1,097.4868	$1,097.49	$1,097.45	$1,097.50