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	$133.84	7.141%	$143.3975	$143.40	$143.40	$143.40
Purchase #2	$133.56	13.511%	$151.6053	$151.61	$151.60	$151.60
Purchase #3	$45.26	3.215%	$46.7151	$46.72	$46.70	$46.70
Purchase #4	$50.71	8.358%	$54.9483	$54.95	$54.95	$54.90
Purchase #5	$6.48	12.247%	$7.2736	$7.27	$7.25	$7.30
Purchase #6	$174.43	7.715%	$187.8873	$187.89	$187.90	$187.90
Purchase #7	$50.40	12.317%	$56.6078	$56.61	$56.60	$56.60
7 purchase totals =	$594.68		$648.4349	$648.45	$648.40	$648.40