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	$141.79	11.369%	$157.9101	$157.91	$157.90	$157.90
Purchase #2	$206.99	12.572%	$233.0128	$233.01	$233.00	$233.00
Purchase #3	$58.47	12.545%	$65.8051	$65.81	$65.80	$65.80
Purchase #4	$118.87	4.686%	$124.4402	$124.44	$124.45	$124.40
Purchase #5	$113.98	12.584%	$128.3232	$128.32	$128.30	$128.30
Purchase #6	$62.38	6.537%	$66.4578	$66.46	$66.45	$66.50
Purchase #7	$178.95	9.868%	$196.6088	$196.61	$196.60	$196.60
7 purchase totals =	$881.43		$972.5580	$972.56	$972.50	$972.50