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	$121.90	4.166%	$126.9784	$126.98	$127.00	$127.00
Purchase #2	$183.64	3.538%	$190.1372	$190.14	$190.15	$190.10
Purchase #3	$51.29	10.258%	$56.5513	$56.55	$56.55	$56.60
Purchase #4	$154.53	4.286%	$161.1532	$161.15	$161.15	$161.20
Purchase #5	$127.79	12.757%	$144.0922	$144.09	$144.10	$144.10
Purchase #6	$179.47	11.864%	$200.7623	$200.76	$200.75	$200.80
Purchase #7	$55.67	6.837%	$59.4762	$59.48	$59.50	$59.50
7 purchase totals =	$874.29		$939.1508	$939.15	$939.20	$939.30