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	$217.80	13.646%	$247.521	$247.52	$247.50	$247.50
Purchase #2	$131.40	4.826%	$137.7414	$137.74	$137.75	$137.70
Purchase #3	$149.38	3.870%	$155.161	$155.16	$155.15	$155.20
Purchase #4	$204.26	9.323%	$223.3032	$223.30	$223.30	$223.30
Purchase #5	$46.71	4.691%	$48.9012	$48.90	$48.90	$48.90
Purchase #6	$136.84	7.135%	$146.6035	$146.60	$146.60	$146.60
Purchase #7	$93.43	7.287%	$100.2382	$100.24	$100.25	$100.20
7 purchase totals =	$979.82		$1,059.4695	$1,059.46	$1,059.45	$1,059.40