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	$135.34	6.671%	$144.3685	$144.37	$144.35	$144.40
Purchase #2	$46.59	10.732%	$51.59	$51.59	$51.60	$51.60
Purchase #3	$201.45	5.175%	$211.875	$211.88	$211.90	$211.90
Purchase #4	$151.50	8.473%	$164.3366	$164.34	$164.35	$164.30
Purchase #5	$11.66	7.638%	$12.5506	$12.55	$12.55	$12.60
Purchase #6	$191.79	6.587%	$204.4232	$204.42	$204.40	$204.40
Purchase #7	$248.54	12.675%	$280.0424	$280.04	$280.05	$280.00
7 purchase totals =	$986.87		$1,069.1863	$1,069.19	$1,069.20	$1,069.20