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	$90.82	10.512%	$100.367	$100.37	$100.35	$100.40
Purchase #2	$12.89	8.230%	$13.9508	$13.95	$13.95	$14.00
Purchase #3	$127.64	4.602%	$133.514	$133.51	$133.50	$133.50
Purchase #4	$41.52	12.338%	$46.6427	$46.64	$46.65	$46.60
Purchase #5	$196.45	9.495%	$215.1029	$215.10	$215.10	$215.10
Purchase #6	$207.60	8.619%	$225.493	$225.49	$225.50	$225.50
Purchase #7	$65.69	11.840%	$73.4677	$73.47	$73.45	$73.50
7 purchase totals =	$742.61		$808.5381	$808.53	$808.50	$808.60