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	$159.31	6.597%	$169.8197	$169.82	$169.80	$169.80
Purchase #2	$230.66	12.395%	$259.2503	$259.25	$259.25	$259.30
Purchase #3	$143.43	8.498%	$155.6187	$155.62	$155.60	$155.60
Purchase #4	$126.73	10.143%	$139.5842	$139.58	$139.60	$139.60
Purchase #5	$100.65	10.770%	$111.49	$111.49	$111.50	$111.50
Purchase #6	$130.61	13.206%	$147.8584	$147.86	$147.85	$147.90
Purchase #7	$38.90	6.608%	$41.4705	$41.47	$41.45	$41.50
7 purchase totals =	$930.29		$1,025.0918	$1,025.09	$1,025.05	$1,025.20