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	$131.81	3.495%	$136.4168	$136.42	$136.40	$136.40
Purchase #2	$65.29	10.433%	$72.1017	$72.10	$72.10	$72.10
Purchase #3	$239.56	6.648%	$255.4859	$255.49	$255.50	$255.50
Purchase #4	$140.62	3.289%	$145.245	$145.25	$145.25	$145.20
Purchase #5	$125.39	5.348%	$132.0959	$132.10	$132.10	$132.10
Purchase #6	$208.90	3.123%	$215.4239	$215.42	$215.40	$215.40
Purchase #7	$237.52	4.201%	$247.4982	$247.50	$247.50	$247.50
7 purchase totals =	$1,149.09		$1,204.2674	$1,204.28	$1,204.25	$1,204.20