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	$105.99	10.297%	$116.9038	$116.90	$116.90	$116.90
Purchase #2	$78.91	5.272%	$83.0701	$83.07	$83.05	$83.10
Purchase #3	$245.40	6.285%	$260.8234	$260.82	$260.80	$260.80
Purchase #4	$191.66	4.536%	$200.3537	$200.35	$200.35	$200.40
Purchase #5	$146.98	5.795%	$155.4975	$155.50	$155.50	$155.50
Purchase #6	$60.81	13.292%	$68.8929	$68.89	$68.90	$68.90
Purchase #7	$73.48	11.592%	$81.9978	$82.00	$82.00	$82.00
7 purchase totals =	$903.23		$967.5392	$967.53	$967.50	$967.60