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	$62.46	4.181%	$65.0715	$65.07	$65.05	$65.10
Purchase #2	$63.89	13.196%	$72.3209	$72.32	$72.30	$72.30
Purchase #3	$195.28	8.748%	$212.3631	$212.36	$212.35	$212.40
Purchase #4	$18.28	5.396%	$19.2664	$19.27	$19.25	$19.30
Purchase #5	$124.68	6.130%	$132.3229	$132.32	$132.30	$132.30
Purchase #6	$24.78	12.104%	$27.7794	$27.78	$27.80	$27.80
Purchase #7	$249.48	10.817%	$276.4663	$276.47	$276.45	$276.50
7 purchase totals =	$738.85		$805.5905	$805.59	$805.50	$805.70