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	$12.61	13.461%	$14.3074	$14.31	$14.30	$14.30
Purchase #2	$143.37	5.228%	$150.8654	$150.87	$150.85	$150.90
Purchase #3	$6.86	8.396%	$7.436	$7.44	$7.45	$7.40
Purchase #4	$11.76	5.298%	$12.383	$12.38	$12.40	$12.40
Purchase #5	$236.38	12.475%	$265.8684	$265.87	$265.85	$265.90
Purchase #6	$105.75	5.481%	$111.5462	$111.55	$111.55	$111.50
Purchase #7	$65.70	4.235%	$68.4824	$68.48	$68.50	$68.50
7 purchase totals =	$582.43		$630.8888	$630.90	$630.90	$630.90