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	$124.50	8.438%	$135.0053	$135.01	$135.00	$135.00
Purchase #2	$103.26	7.549%	$111.0551	$111.06	$111.05	$111.10
Purchase #3	$140.67	5.623%	$148.5799	$148.58	$148.60	$148.60
Purchase #4	$205.66	12.264%	$230.8821	$230.88	$230.90	$230.90
Purchase #5	$176.59	13.720%	$200.8181	$200.82	$200.80	$200.80
Purchase #6	$194.53	7.683%	$209.4757	$209.48	$209.50	$209.50
Purchase #7	$23.47	10.298%	$25.8869	$25.89	$25.90	$25.90
7 purchase totals =	$968.68		$1,061.7031	$1,061.72	$1,061.75	$1,061.80