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	$221.26	3.147%	$228.2231	$228.22	$228.20	$228.20
Purchase #2	$95.67	10.237%	$105.4637	$105.46	$105.45	$105.50
Purchase #3	$52.52	7.348%	$56.3792	$56.38	$56.40	$56.40
Purchase #4	$7.46	5.551%	$7.8741	$7.87	$7.85	$7.90
Purchase #5	$95.52	11.517%	$106.521	$106.52	$106.50	$106.50
Purchase #6	$168.86	12.705%	$190.3137	$190.31	$190.30	$190.30
Purchase #7	$101.66	5.125%	$106.8701	$106.87	$106.85	$106.90
7 purchase totals =	$742.95		$801.6449	$801.63	$801.55	$801.70