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	$57.54	8.768%	$62.5851	$62.59	$62.60	$62.60
Purchase #2	$154.86	4.205%	$161.3719	$161.37	$161.35	$161.40
Purchase #3	$113.89	11.526%	$127.017	$127.02	$127.00	$127.00
Purchase #4	$139.61	6.682%	$148.9387	$148.94	$148.95	$148.90
Purchase #5	$34.80	3.214%	$35.9185	$35.92	$35.90	$35.90
Purchase #6	$221.58	11.825%	$247.7818	$247.78	$247.80	$247.80
Purchase #7	$246.86	13.400%	$279.9392	$279.94	$279.95	$279.90
7 purchase totals =	$969.14		$1,063.5522	$1,063.56	$1,063.55	$1,063.50