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	$67.47	4.732%	$70.6627	$70.66	$70.65	$70.70
Purchase #2	$68.25	9.114%	$74.4703	$74.47	$74.45	$74.50
Purchase #3	$246.63	11.834%	$275.8162	$275.82	$275.80	$275.80
Purchase #4	$249.92	8.849%	$272.0354	$272.04	$272.05	$272.00
Purchase #5	$32.92	7.342%	$35.337	$35.34	$35.35	$35.30
Purchase #6	$146.72	9.309%	$160.3782	$160.38	$160.40	$160.40
Purchase #7	$248.61	5.699%	$262.7783	$262.78	$262.80	$262.80
7 purchase totals =	$1,060.52		$1,151.4781	$1,151.49	$1,151.50	$1,151.50