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	$162.83	8.607%	$176.8448	$176.84	$176.85	$176.80
Purchase #2	$127.72	12.162%	$143.2533	$143.25	$143.25	$143.30
Purchase #3	$91.91	6.355%	$97.7509	$97.75	$97.75	$97.80
Purchase #4	$189.91	13.491%	$215.5308	$215.53	$215.55	$215.50
Purchase #5	$103.94	4.518%	$108.636	$108.64	$108.65	$108.60
Purchase #6	$102.86	8.435%	$111.5362	$111.54	$111.55	$111.50
Purchase #7	$43.81	10.211%	$48.2834	$48.28	$48.30	$48.30
7 purchase totals =	$822.98		$901.8354	$901.83	$901.90	$901.80