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	$104.69	12.123%	$117.3816	$117.38	$117.40	$117.40
Purchase #2	$87.52	5.778%	$92.5769	$92.58	$92.60	$92.60
Purchase #3	$195.78	5.233%	$206.0252	$206.03	$206.05	$206.00
Purchase #4	$157.81	5.794%	$166.9535	$166.95	$166.95	$167.00
Purchase #5	$40.70	7.348%	$43.6906	$43.69	$43.70	$43.70
Purchase #6	$174.56	4.788%	$182.9179	$182.92	$182.90	$182.90
Purchase #7	$231.55	10.496%	$255.8535	$255.85	$255.85	$255.90
7 purchase totals =	$992.61		$1,065.3992	$1,065.40	$1,065.45	$1,065.50