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	$53.52	11.710%	$59.7872	$59.79	$59.80	$59.80
Purchase #2	$169.39	9.321%	$185.1788	$185.18	$185.20	$185.20
Purchase #3	$208.39	11.531%	$232.4195	$232.42	$232.40	$232.40
Purchase #4	$231.66	11.385%	$258.0345	$258.03	$258.05	$258.00
Purchase #5	$41.58	6.271%	$44.1875	$44.19	$44.20	$44.20
Purchase #6	$94.65	12.456%	$106.4396	$106.44	$106.45	$106.40
Purchase #7	$73.47	6.872%	$78.5189	$78.52	$78.50	$78.50
7 purchase totals =	$872.66		$964.5660	$964.57	$964.60	$964.50