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	$155.99	8.579%	$169.3724	$169.37	$169.35	$169.40
Purchase #2	$11.91	11.232%	$13.2477	$13.25	$13.25	$13.20
Purchase #3	$187.80	6.223%	$199.4868	$199.49	$199.50	$199.50
Purchase #4	$95.52	4.856%	$100.1585	$100.16	$100.15	$100.20
Purchase #5	$128.50	10.229%	$141.6443	$141.64	$141.65	$141.60
Purchase #6	$244.46	12.471%	$274.9466	$274.95	$274.95	$274.90
Purchase #7	$97.85	6.517%	$104.2269	$104.23	$104.25	$104.20
7 purchase totals =	$922.03		$1,003.0832	$1,003.09	$1,003.10	$1,003.00