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	$66.32	9.560%	$72.6602	$72.66	$72.65	$72.70
Purchase #2	$49.68	13.285%	$56.28	$56.28	$56.30	$56.30
Purchase #3	$12.45	13.640%	$14.1482	$14.15	$14.15	$14.10
Purchase #4	$219.83	9.390%	$240.472	$240.47	$240.45	$240.50
Purchase #5	$50.40	10.820%	$55.8533	$55.85	$55.85	$55.90
Purchase #6	$34.58	7.778%	$37.2696	$37.27	$37.25	$37.30
Purchase #7	$84.64	10.726%	$93.7185	$93.72	$93.70	$93.70
7 purchase totals =	$517.90		$570.4018	$570.40	$570.35	$570.50