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	$222.60	7.267%	$238.7763	$238.78	$238.80	$238.80
Purchase #2	$24.71	8.641%	$26.8452	$26.85	$26.85	$26.80
Purchase #3	$58.98	6.514%	$62.822	$62.82	$62.80	$62.80
Purchase #4	$233.87	9.630%	$256.3917	$256.39	$256.40	$256.40
Purchase #5	$11.82	12.554%	$13.3039	$13.30	$13.30	$13.30
Purchase #6	$158.38	10.732%	$175.3773	$175.38	$175.40	$175.40
Purchase #7	$167.51	6.516%	$178.425	$178.43	$178.45	$178.40
7 purchase totals =	$877.87		$951.9414	$951.95	$952.00	$951.90