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	$115.60	10.504%	$127.7426	$127.74	$127.75	$127.70
Purchase #2	$173.87	7.605%	$187.0928	$187.09	$187.10	$187.10
Purchase #3	$77.85	7.255%	$83.498	$83.50	$83.50	$83.50
Purchase #4	$95.65	8.856%	$104.1208	$104.12	$104.10	$104.10
Purchase #5	$96.86	3.749%	$100.4913	$100.49	$100.50	$100.50
Purchase #6	$189.45	4.800%	$198.5436	$198.54	$198.55	$198.50
Purchase #7	$17.99	9.604%	$19.7178	$19.72	$19.70	$19.70
7 purchase totals =	$767.27		$821.2069	$821.20	$821.20	$821.10