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	$148.39	7.335%	$159.2744	$159.27	$159.25	$159.30
Purchase #2	$24.45	9.756%	$26.8353	$26.84	$26.85	$26.80
Purchase #3	$237.61	3.181%	$245.1684	$245.17	$245.15	$245.20
Purchase #4	$117.59	5.364%	$123.8975	$123.90	$123.90	$123.90
Purchase #5	$115.50	12.763%	$130.2413	$130.24	$130.25	$130.20
Purchase #6	$75.64	3.803%	$78.5166	$78.52	$78.50	$78.50
Purchase #7	$239.89	8.340%	$259.8968	$259.90	$259.90	$259.90
7 purchase totals =	$959.07		$1,023.8303	$1,023.84	$1,023.80	$1,023.80