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	$84.39	13.591%	$95.8594	$95.86	$95.85	$95.90
Purchase #2	$52.29	6.659%	$55.772	$55.77	$55.75	$55.80
Purchase #3	$8.69	12.807%	$9.8029	$9.80	$9.80	$9.80
Purchase #4	$199.85	7.647%	$215.1325	$215.13	$215.15	$215.10
Purchase #5	$82.40	8.477%	$89.385	$89.39	$89.40	$89.40
Purchase #6	$117.82	12.836%	$132.9434	$132.94	$132.95	$132.90
Purchase #7	$89.50	8.870%	$97.4387	$97.44	$97.45	$97.40
7 purchase totals =	$634.94		$696.3339	$696.33	$696.35	$696.30