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	$101.42	4.358%	$105.8399	$105.84	$105.85	$105.80
Purchase #2	$104.80	11.542%	$116.896	$116.90	$116.90	$116.90
Purchase #3	$95.51	8.591%	$103.7153	$103.72	$103.70	$103.70
Purchase #4	$104.75	13.527%	$118.9195	$118.92	$118.90	$118.90
Purchase #5	$210.77	5.697%	$222.7776	$222.78	$222.80	$222.80
Purchase #6	$75.28	4.688%	$78.8091	$78.81	$78.80	$78.80
Purchase #7	$15.94	5.479%	$16.8134	$16.81	$16.80	$16.80
7 purchase totals =	$708.47		$763.7708	$763.78	$763.75	$763.70