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	$137.31	4.333%	$143.2596	$143.26	$143.25	$143.30
Purchase #2	$141.99	5.860%	$150.3106	$150.31	$150.30	$150.30
Purchase #3	$16.27	3.869%	$16.8995	$16.90	$16.90	$16.90
Purchase #4	$247.65	4.545%	$258.9057	$258.91	$258.90	$258.90
Purchase #5	$62.91	13.834%	$71.613	$71.61	$71.60	$71.60
Purchase #6	$34.85	12.783%	$39.3049	$39.30	$39.30	$39.30
Purchase #7	$35.39	8.679%	$38.4615	$38.46	$38.45	$38.50
7 purchase totals =	$676.37		$718.7548	$718.75	$718.70	$718.80