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	$242.75	7.349%	$260.5897	$260.59	$260.60	$260.60
Purchase #2	$214.34	3.794%	$222.4721	$222.47	$222.45	$222.50
Purchase #3	$169.48	11.430%	$188.8516	$188.85	$188.85	$188.90
Purchase #4	$56.81	10.602%	$62.833	$62.83	$62.85	$62.80
Purchase #5	$126.54	13.485%	$143.6039	$143.60	$143.60	$143.60
Purchase #6	$238.33	4.354%	$248.7069	$248.71	$248.70	$248.70
Purchase #7	$38.87	12.409%	$43.6934	$43.69	$43.70	$43.70
7 purchase totals =	$1,087.12		$1,170.7506	$1,170.74	$1,170.75	$1,170.80