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	$61.90	5.790%	$65.484	$65.48	$65.50	$65.50
Purchase #2	$208.27	6.303%	$221.3973	$221.40	$221.40	$221.40
Purchase #3	$244.41	4.370%	$255.0907	$255.09	$255.10	$255.10
Purchase #4	$208.58	5.795%	$220.6672	$220.67	$220.65	$220.70
Purchase #5	$181.72	10.302%	$200.4408	$200.44	$200.45	$200.40
Purchase #6	$204.30	10.845%	$226.4563	$226.46	$226.45	$226.50
Purchase #7	$215.64	12.175%	$241.8942	$241.89	$241.90	$241.90
7 purchase totals =	$1,324.82		$1,431.4305	$1,431.43	$1,431.45	$1,431.50