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	$32.59	11.724%	$36.4109	$36.41	$36.40	$36.40
Purchase #2	$149.59	6.189%	$158.8481	$158.85	$158.85	$158.80
Purchase #3	$103.59	7.779%	$111.6483	$111.65	$111.65	$111.60
Purchase #4	$18.95	13.696%	$21.5454	$21.55	$21.55	$21.50
Purchase #5	$109.64	12.643%	$123.5018	$123.50	$123.50	$123.50
Purchase #6	$208.43	12.186%	$233.8293	$233.83	$233.85	$233.80
Purchase #7	$33.90	4.524%	$35.4336	$35.43	$35.45	$35.40
7 purchase totals =	$656.69		$721.2174	$721.22	$721.25	$721.00