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	$113.59	10.667%	$125.7066	$125.71	$125.70	$125.70
Purchase #2	$173.82	7.497%	$186.8513	$186.85	$186.85	$186.90
Purchase #3	$67.56	13.844%	$76.913	$76.91	$76.90	$76.90
Purchase #4	$221.46	9.281%	$242.0137	$242.01	$242.00	$242.00
Purchase #5	$63.78	4.278%	$66.5085	$66.51	$66.50	$66.50
Purchase #6	$39.60	13.576%	$44.9761	$44.98	$45.00	$45.00
Purchase #7	$170.49	11.806%	$190.618	$190.62	$190.60	$190.60
7 purchase totals =	$850.30		$933.5872	$933.59	$933.55	$933.60