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	$200.29	10.195%	$220.7096	$220.71	$220.70	$220.70
Purchase #2	$65.53	9.723%	$71.9015	$71.90	$71.90	$71.90
Purchase #3	$68.25	6.795%	$72.8876	$72.89	$72.90	$72.90
Purchase #4	$197.72	12.112%	$221.6678	$221.67	$221.65	$221.70
Purchase #5	$186.25	13.860%	$212.0643	$212.06	$212.05	$212.10
Purchase #6	$6.33	8.495%	$6.8677	$6.87	$6.85	$6.90
Purchase #7	$45.34	10.688%	$50.1859	$50.19	$50.20	$50.20
7 purchase totals =	$769.71		$856.2844	$856.29	$856.25	$856.40