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	$139.87	6.134%	$148.4496	$148.45	$148.45	$148.40
Purchase #2	$23.66	3.157%	$24.4069	$24.41	$24.40	$24.40
Purchase #3	$131.84	6.849%	$140.8697	$140.87	$140.85	$140.90
Purchase #4	$215.45	11.842%	$240.9636	$240.96	$240.95	$241.00
Purchase #5	$236.37	8.545%	$256.5678	$256.57	$256.55	$256.60
Purchase #6	$176.59	13.606%	$200.6168	$200.62	$200.60	$200.60
Purchase #7	$19.46	11.553%	$21.7082	$21.71	$21.70	$21.70
7 purchase totals =	$943.24		$1,033.5826	$1,033.59	$1,033.50	$1,033.60