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	$57.25	9.306%	$62.5777	$62.58	$62.60	$62.60
Purchase #2	$173.49	3.471%	$179.5118	$179.51	$179.50	$179.50
Purchase #3	$193.90	13.462%	$220.0028	$220.00	$220.00	$220.00
Purchase #4	$219.78	13.337%	$249.0921	$249.09	$249.10	$249.10
Purchase #5	$89.33	12.462%	$100.4623	$100.46	$100.45	$100.50
Purchase #6	$124.40	12.244%	$139.6315	$139.63	$139.65	$139.60
Purchase #7	$190.95	9.864%	$209.7853	$209.79	$209.80	$209.80
7 purchase totals =	$1,049.10		$1,161.0635	$1,161.06	$1,161.10	$1,161.10