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	$48.70	10.751%	$53.9357	$53.94	$53.95	$53.90
Purchase #2	$223.53	3.763%	$231.9414	$231.94	$231.95	$231.90
Purchase #3	$153.60	4.561%	$160.6057	$160.61	$160.60	$160.60
Purchase #4	$63.39	13.577%	$71.9965	$72.00	$72.00	$72.00
Purchase #5	$29.67	8.144%	$32.0863	$32.09	$32.10	$32.10
Purchase #6	$190.59	12.290%	$214.0135	$214.01	$214.00	$214.00
Purchase #7	$138.78	3.205%	$143.2279	$143.23	$143.25	$143.20
7 purchase totals =	$848.26		$907.8070	$907.82	$907.85	$907.70