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	$206.75	10.493%	$228.4443	$228.44	$228.45	$228.40
Purchase #2	$98.72	6.789%	$105.4221	$105.42	$105.40	$105.40
Purchase #3	$94.80	4.626%	$99.1854	$99.19	$99.20	$99.20
Purchase #4	$71.31	11.520%	$79.5249	$79.52	$79.50	$79.50
Purchase #5	$57.81	5.340%	$60.8971	$60.90	$60.90	$60.90
Purchase #6	$82.51	3.801%	$85.6462	$85.65	$85.65	$85.60
Purchase #7	$73.90	13.580%	$83.9356	$83.94	$83.95	$83.90
7 purchase totals =	$685.80		$743.0556	$743.06	$743.05	$742.90