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	$107.52	12.139%	$120.5719	$120.57	$120.55	$120.60
Purchase #2	$37.70	7.442%	$40.5056	$40.51	$40.50	$40.50
Purchase #3	$79.68	5.357%	$83.9485	$83.95	$83.95	$83.90
Purchase #4	$133.61	7.581%	$143.739	$143.74	$143.75	$143.70
Purchase #5	$75.46	6.706%	$80.5203	$80.52	$80.50	$80.50
Purchase #6	$32.38	5.428%	$34.1376	$34.14	$34.15	$34.10
Purchase #7	$196.57	9.692%	$215.6216	$215.62	$215.60	$215.60
7 purchase totals =	$662.92		$719.0445	$719.05	$719.00	$718.90