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	$240.89	9.102%	$262.8158	$262.82	$262.80	$262.80
Purchase #2	$222.67	8.715%	$242.0757	$242.08	$242.10	$242.10
Purchase #3	$88.56	6.750%	$94.5378	$94.54	$94.55	$94.50
Purchase #4	$174.27	9.841%	$191.4199	$191.42	$191.40	$191.40
Purchase #5	$93.93	6.868%	$100.3811	$100.38	$100.40	$100.40
Purchase #6	$121.54	12.480%	$136.7082	$136.71	$136.70	$136.70
Purchase #7	$132.55	6.210%	$140.7814	$140.78	$140.80	$140.80
7 purchase totals =	$1,074.41		$1,168.7199	$1,168.73	$1,168.75	$1,168.70