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	$43.92	9.347%	$48.0252	$48.03	$48.05	$48.00
Purchase #2	$216.51	4.333%	$225.8914	$225.89	$225.90	$225.90
Purchase #3	$103.31	7.691%	$111.2556	$111.26	$111.25	$111.30
Purchase #4	$66.45	6.740%	$70.9287	$70.93	$70.95	$70.90
Purchase #5	$102.66	13.802%	$116.8291	$116.83	$116.85	$116.80
Purchase #6	$29.45	8.641%	$31.9948	$31.99	$32.00	$32.00
Purchase #7	$43.32	10.453%	$47.8482	$47.85	$47.85	$47.80
7 purchase totals =	$605.62		$652.7730	$652.78	$652.85	$652.70