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	$66.82	8.320%	$72.3794	$72.38	$72.40	$72.40
Purchase #2	$21.25	9.185%	$23.2018	$23.20	$23.20	$23.20
Purchase #3	$93.67	5.330%	$98.6626	$98.66	$98.65	$98.70
Purchase #4	$46.62	11.821%	$52.131	$52.13	$52.15	$52.10
Purchase #5	$137.53	4.326%	$143.4795	$143.48	$143.50	$143.50
Purchase #6	$191.48	10.748%	$212.0603	$212.06	$212.05	$212.10
Purchase #7	$59.56	10.638%	$65.896	$65.90	$65.90	$65.90
7 purchase totals =	$616.93		$667.8106	$667.81	$667.85	$667.90