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	$128.67	11.549%	$143.5301	$143.53	$143.55	$143.50
Purchase #2	$15.33	3.697%	$15.8968	$15.90	$15.90	$15.90
Purchase #3	$50.38	9.660%	$55.2467	$55.25	$55.25	$55.20
Purchase #4	$202.77	9.385%	$221.8	$221.80	$221.80	$221.80
Purchase #5	$58.67	13.277%	$66.4596	$66.46	$66.45	$66.50
Purchase #6	$68.43	13.253%	$77.499	$77.50	$77.50	$77.50
Purchase #7	$174.86	7.211%	$187.4692	$187.47	$187.45	$187.50
7 purchase totals =	$699.11		$767.9014	$767.91	$767.90	$767.90