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	$121.91	8.335%	$132.0712	$132.07	$132.05	$132.10
Purchase #2	$95.65	13.149%	$108.227	$108.23	$108.25	$108.20
Purchase #3	$56.59	13.606%	$64.2896	$64.29	$64.30	$64.30
Purchase #4	$82.72	8.473%	$89.7289	$89.73	$89.75	$89.70
Purchase #5	$56.51	11.392%	$62.9476	$62.95	$62.95	$62.90
Purchase #6	$167.49	13.480%	$190.0677	$190.07	$190.05	$190.10
Purchase #7	$187.92	13.257%	$212.8326	$212.83	$212.85	$212.80
7 purchase totals =	$768.79		$860.1646	$860.17	$860.20	$860.10