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	$96.79	13.676%	$110.027	$110.03	$110.05	$110.00
Purchase #2	$88.50	8.156%	$95.7181	$95.72	$95.70	$95.70
Purchase #3	$131.79	8.815%	$143.4073	$143.41	$143.40	$143.40
Purchase #4	$84.25	6.485%	$89.7136	$89.71	$89.70	$89.70
Purchase #5	$138.93	10.694%	$153.7872	$153.79	$153.80	$153.80
Purchase #6	$50.52	6.559%	$53.8336	$53.83	$53.85	$53.80
Purchase #7	$38.68	3.105%	$39.881	$39.88	$39.90	$39.90
7 purchase totals =	$629.46		$686.3678	$686.37	$686.40	$686.30