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	$50.28	4.700%	$52.6432	$52.64	$52.65	$52.60
Purchase #2	$105.37	13.126%	$119.2009	$119.20	$119.20	$119.20
Purchase #3	$221.75	5.496%	$233.9374	$233.94	$233.95	$233.90
Purchase #4	$49.84	11.804%	$55.7231	$55.72	$55.70	$55.70
Purchase #5	$65.83	10.206%	$72.5486	$72.55	$72.55	$72.50
Purchase #6	$249.51	5.166%	$262.3997	$262.40	$262.40	$262.40
Purchase #7	$159.27	10.851%	$176.5524	$176.55	$176.55	$176.60
7 purchase totals =	$901.85		$973.0053	$973.00	$973.00	$972.90