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	$216.78	11.656%	$242.0479	$242.05	$242.05	$242.00
Purchase #2	$207.62	12.233%	$233.0182	$233.02	$233.00	$233.00
Purchase #3	$40.41	3.622%	$41.8737	$41.87	$41.85	$41.90
Purchase #4	$69.73	8.842%	$75.8955	$75.90	$75.90	$75.90
Purchase #5	$31.95	4.750%	$33.4676	$33.47	$33.45	$33.50
Purchase #6	$105.79	5.733%	$111.8549	$111.85	$111.85	$111.90
Purchase #7	$75.94	10.473%	$83.8932	$83.89	$83.90	$83.90
7 purchase totals =	$748.22		$822.0510	$822.05	$822.00	$822.10