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	$55.57	7.718%	$59.8589	$59.86	$59.85	$59.90
Purchase #2	$196.56	4.297%	$205.0062	$205.01	$205.00	$205.00
Purchase #3	$169.77	9.834%	$186.4652	$186.47	$186.45	$186.50
Purchase #4	$94.43	11.832%	$105.603	$105.60	$105.60	$105.60
Purchase #5	$21.52	8.298%	$23.3057	$23.31	$23.30	$23.30
Purchase #6	$11.48	8.525%	$12.4587	$12.46	$12.45	$12.50
Purchase #7	$38.89	5.520%	$41.0367	$41.04	$41.05	$41.00
7 purchase totals =	$588.22		$633.7344	$633.75	$633.70	$633.80