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	$173.30	8.272%	$187.6354	$187.64	$187.65	$187.60
Purchase #2	$67.71	9.456%	$74.1127	$74.11	$74.10	$74.10
Purchase #3	$137.85	10.422%	$152.2167	$152.22	$152.20	$152.20
Purchase #4	$59.95	5.244%	$63.0938	$63.09	$63.10	$63.10
Purchase #5	$28.52	13.316%	$32.3177	$32.32	$32.30	$32.30
Purchase #6	$187.84	4.426%	$196.1538	$196.15	$196.15	$196.20
Purchase #7	$230.50	10.866%	$255.5461	$255.55	$255.55	$255.50
7 purchase totals =	$885.67		$961.0762	$961.08	$961.05	$961.00