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	$143.96	4.812%	$150.8874	$150.89	$150.90	$150.90
Purchase #2	$105.93	5.156%	$111.3918	$111.39	$111.40	$111.40
Purchase #3	$67.99	7.143%	$72.8465	$72.85	$72.85	$72.80
Purchase #4	$208.34	8.509%	$226.0677	$226.07	$226.05	$226.10
Purchase #5	$66.78	9.209%	$72.9298	$72.93	$72.95	$72.90
Purchase #6	$16.66	4.328%	$17.381	$17.38	$17.40	$17.40
Purchase #7	$74.44	3.721%	$77.2099	$77.21	$77.20	$77.20
7 purchase totals =	$684.10		$728.7141	$728.72	$728.75	$728.70