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	$147.29	8.467%	$159.761	$159.76	$159.75	$159.80
Purchase #2	$136.89	13.265%	$155.0485	$155.05	$155.05	$155.00
Purchase #3	$114.86	11.189%	$127.7117	$127.71	$127.70	$127.70
Purchase #4	$217.29	13.381%	$246.3656	$246.37	$246.35	$246.40
Purchase #5	$37.29	13.832%	$42.448	$42.45	$42.45	$42.40
Purchase #6	$29.54	13.491%	$33.5252	$33.53	$33.55	$33.50
Purchase #7	$16.53	5.660%	$17.4656	$17.47	$17.45	$17.50
7 purchase totals =	$699.69		$782.3256	$782.34	$782.30	$782.30