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	$201.84	10.227%	$222.4822	$222.48	$222.50	$222.50
Purchase #2	$6.77	11.761%	$7.5662	$7.57	$7.55	$7.60
Purchase #3	$68.90	13.515%	$78.2118	$78.21	$78.20	$78.20
Purchase #4	$188.74	6.348%	$200.7212	$200.72	$200.70	$200.70
Purchase #5	$47.54	8.763%	$51.7059	$51.71	$51.70	$51.70
Purchase #6	$19.83	8.542%	$21.5239	$21.52	$21.50	$21.50
Purchase #7	$172.72	10.636%	$191.0905	$191.09	$191.10	$191.10
7 purchase totals =	$706.34		$773.3017	$773.30	$773.25	$773.30