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	$64.50	3.804%	$66.9536	$66.95	$66.95	$67.00
Purchase #2	$176.53	4.737%	$184.8922	$184.89	$184.90	$184.90
Purchase #3	$158.58	11.276%	$176.4615	$176.46	$176.45	$176.50
Purchase #4	$176.72	7.542%	$190.0482	$190.05	$190.05	$190.00
Purchase #5	$77.92	4.727%	$81.6033	$81.60	$81.60	$81.60
Purchase #6	$206.54	4.457%	$215.7455	$215.75	$215.75	$215.70
Purchase #7	$47.50	10.751%	$52.6067	$52.61	$52.60	$52.60
7 purchase totals =	$908.29		$968.3110	$968.31	$968.30	$968.30