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	$14.96	11.273%	$16.6464	$16.65	$16.65	$16.60
Purchase #2	$18.99	7.599%	$20.4331	$20.43	$20.45	$20.40
Purchase #3	$215.59	5.607%	$227.6781	$227.68	$227.70	$227.70
Purchase #4	$38.86	12.589%	$43.7521	$43.75	$43.75	$43.80
Purchase #5	$206.50	9.835%	$226.8093	$226.81	$226.80	$226.80
Purchase #6	$142.81	6.148%	$151.59	$151.59	$151.60	$151.60
Purchase #7	$89.72	11.353%	$99.9059	$99.91	$99.90	$99.90
7 purchase totals =	$727.43		$786.8149	$786.82	$786.85	$786.80