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	$100.31	3.198%	$103.5179	$103.52	$103.50	$103.50
Purchase #2	$11.31	8.185%	$12.2357	$12.24	$12.25	$12.20
Purchase #3	$227.41	10.834%	$252.0476	$252.05	$252.05	$252.00
Purchase #4	$221.84	7.176%	$237.7592	$237.76	$237.75	$237.80
Purchase #5	$112.89	13.339%	$127.9484	$127.95	$127.95	$127.90
Purchase #6	$194.61	9.844%	$213.7674	$213.77	$213.75	$213.80
Purchase #7	$63.52	11.246%	$70.6635	$70.66	$70.65	$70.70
7 purchase totals =	$931.89		$1,017.9397	$1,017.95	$1,017.90	$1,017.90