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	$141.97	6.534%	$151.2463	$151.25	$151.25	$151.20
Purchase #2	$109.89	3.786%	$114.0504	$114.05	$114.05	$114.10
Purchase #3	$37.67	7.158%	$40.3664	$40.37	$40.35	$40.40
Purchase #4	$140.76	13.734%	$160.092	$160.09	$160.10	$160.10
Purchase #5	$81.86	12.494%	$92.0876	$92.09	$92.10	$92.10
Purchase #6	$126.35	4.335%	$131.8273	$131.83	$131.85	$131.80
Purchase #7	$116.87	10.237%	$128.834	$128.83	$128.85	$128.80
7 purchase totals =	$755.37		$818.5040	$818.51	$818.55	$818.50