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	$46.80	10.391%	$51.663	$51.66	$51.65	$51.70
Purchase #2	$93.85	6.256%	$99.7213	$99.72	$99.70	$99.70
Purchase #3	$55.28	11.794%	$61.7997	$61.80	$61.80	$61.80
Purchase #4	$41.93	11.550%	$46.7729	$46.77	$46.75	$46.80
Purchase #5	$114.27	10.499%	$126.2672	$126.27	$126.25	$126.30
Purchase #6	$63.52	13.358%	$72.005	$72.01	$72.00	$72.00
Purchase #7	$148.64	4.815%	$155.797	$155.80	$155.80	$155.80
7 purchase totals =	$564.29		$614.0261	$614.03	$613.95	$614.10