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	$137.28	12.846%	$154.915	$154.92	$154.90	$154.90
Purchase #2	$140.58	5.466%	$148.2641	$148.26	$148.25	$148.30
Purchase #3	$81.96	4.859%	$85.9424	$85.94	$85.95	$85.90
Purchase #4	$167.48	9.538%	$183.4542	$183.45	$183.45	$183.50
Purchase #5	$157.32	13.361%	$178.3395	$178.34	$178.35	$178.30
Purchase #6	$133.99	13.507%	$152.088	$152.09	$152.10	$152.10
Purchase #7	$126.31	8.845%	$137.4821	$137.48	$137.50	$137.50
7 purchase totals =	$944.92		$1,040.4853	$1,040.48	$1,040.50	$1,040.50