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	$105.92	5.604%	$111.8558	$111.86	$111.85	$111.90
Purchase #2	$85.89	5.600%	$90.6998	$90.70	$90.70	$90.70
Purchase #3	$130.59	9.783%	$143.3656	$143.37	$143.35	$143.40
Purchase #4	$131.49	10.782%	$145.6673	$145.67	$145.65	$145.70
Purchase #5	$87.93	3.525%	$91.0295	$91.03	$91.05	$91.00
Purchase #6	$70.53	5.329%	$74.2885	$74.29	$74.30	$74.30
Purchase #7	$79.28	8.115%	$85.7136	$85.71	$85.70	$85.70
7 purchase totals =	$691.63		$742.6201	$742.63	$742.60	$742.70