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	$108.67	10.334%	$119.9	$119.90	$119.90	$119.90
Purchase #2	$176.85	12.296%	$198.5955	$198.60	$198.60	$198.60
Purchase #3	$5.62	4.149%	$5.8532	$5.85	$5.85	$5.90
Purchase #4	$63.29	13.353%	$71.7411	$71.74	$71.75	$71.70
Purchase #5	$12.26	4.553%	$12.8182	$12.82	$12.80	$12.80
Purchase #6	$177.46	10.725%	$196.4926	$196.49	$196.50	$196.50
Purchase #7	$132.70	8.414%	$143.8654	$143.87	$143.85	$143.90
7 purchase totals =	$676.85		$749.2660	$749.27	$749.25	$749.30