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	$90.52	5.151%	$95.1827	$95.18	$95.20	$95.20
Purchase #2	$248.72	12.792%	$280.5363	$280.54	$280.55	$280.50
Purchase #3	$52.52	4.830%	$55.0567	$55.06	$55.05	$55.10
Purchase #4	$188.58	11.763%	$210.7627	$210.76	$210.75	$210.80
Purchase #5	$247.58	6.208%	$262.9498	$262.95	$262.95	$262.90
Purchase #6	$122.57	3.431%	$126.7754	$126.78	$126.80	$126.80
Purchase #7	$191.89	3.338%	$198.2953	$198.30	$198.30	$198.30
7 purchase totals =	$1,142.38		$1,229.5589	$1,229.57	$1,229.60	$1,229.60