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	$30.39	3.523%	$31.4606	$31.46	$31.45	$31.50
Purchase #2	$94.32	10.357%	$104.0887	$104.09	$104.10	$104.10
Purchase #3	$108.31	9.668%	$118.7814	$118.78	$118.80	$118.80
Purchase #4	$164.92	4.273%	$171.967	$171.97	$171.95	$172.00
Purchase #5	$21.76	4.723%	$22.7877	$22.79	$22.80	$22.80
Purchase #6	$51.92	6.558%	$55.3249	$55.32	$55.30	$55.30
Purchase #7	$202.78	9.743%	$222.5369	$222.54	$222.55	$222.50
7 purchase totals =	$674.40		$726.9472	$726.95	$726.95	$727.00