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	$71.85	13.786%	$81.7552	$81.76	$81.75	$81.80
Purchase #2	$76.45	13.248%	$86.5781	$86.58	$86.60	$86.60
Purchase #3	$175.51	5.567%	$185.2806	$185.28	$185.30	$185.30
Purchase #4	$101.32	4.259%	$105.6352	$105.64	$105.65	$105.60
Purchase #5	$178.50	7.335%	$191.593	$191.59	$191.60	$191.60
Purchase #6	$22.82	4.445%	$23.8343	$23.83	$23.85	$23.80
Purchase #7	$47.63	4.145%	$49.6043	$49.60	$49.60	$49.60
7 purchase totals =	$674.08		$724.2807	$724.28	$724.35	$724.30