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	$80.32	3.135%	$82.838	$82.84	$82.85	$82.80
Purchase #2	$103.43	10.318%	$114.1019	$114.10	$114.10	$114.10
Purchase #3	$203.69	10.246%	$224.5601	$224.56	$224.55	$224.60
Purchase #4	$131.43	6.168%	$139.5366	$139.54	$139.55	$139.50
Purchase #5	$7.76	10.162%	$8.5486	$8.55	$8.55	$8.50
Purchase #6	$176.87	7.740%	$190.5597	$190.56	$190.55	$190.60
Purchase #7	$119.87	4.163%	$124.8602	$124.86	$124.85	$124.90
7 purchase totals =	$823.37		$885.0051	$885.01	$885.00	$885.00