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	$118.82	8.438%	$128.846	$128.85	$128.85	$128.80
Purchase #2	$92.47	8.624%	$100.4446	$100.44	$100.45	$100.40
Purchase #3	$134.75	11.683%	$150.4928	$150.49	$150.50	$150.50
Purchase #4	$128.92	6.623%	$137.4584	$137.46	$137.45	$137.50
Purchase #5	$80.94	10.560%	$89.4873	$89.49	$89.50	$89.50
Purchase #6	$172.29	12.849%	$194.4275	$194.43	$194.45	$194.40
Purchase #7	$136.95	8.652%	$148.7989	$148.80	$148.80	$148.80
7 purchase totals =	$865.14		$949.9555	$949.96	$950.00	$949.90