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	$134.56	12.657%	$151.5913	$151.59	$151.60	$151.60
Purchase #2	$239.81	6.784%	$256.0787	$256.08	$256.10	$256.10
Purchase #3	$220.64	13.709%	$250.8875	$250.89	$250.90	$250.90
Purchase #4	$11.70	4.744%	$12.255	$12.26	$12.25	$12.30
Purchase #5	$181.50	3.487%	$187.8289	$187.83	$187.85	$187.80
Purchase #6	$100.66	12.828%	$113.5727	$113.57	$113.55	$113.60
Purchase #7	$54.28	11.457%	$60.4989	$60.50	$60.50	$60.50
7 purchase totals =	$943.15		$1,032.7130	$1,032.72	$1,032.75	$1,032.80