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	$199.91	9.462%	$218.8255	$218.83	$218.85	$218.80
Purchase #2	$18.74	6.178%	$19.8978	$19.90	$19.90	$19.90
Purchase #3	$67.42	13.179%	$76.3053	$76.31	$76.30	$76.30
Purchase #4	$61.28	13.525%	$69.5681	$69.57	$69.55	$69.60
Purchase #5	$75.89	3.752%	$78.7374	$78.74	$78.75	$78.70
Purchase #6	$129.45	8.523%	$140.483	$140.48	$140.50	$140.50
Purchase #7	$18.34	10.794%	$20.3196	$20.32	$20.30	$20.30
7 purchase totals =	$571.03		$624.1367	$624.15	$624.15	$624.10