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	$128.90	9.746%	$141.4626	$141.46	$141.45	$141.50
Purchase #2	$200.44	11.762%	$224.0158	$224.02	$224.00	$224.00
Purchase #3	$59.60	5.625%	$62.9525	$62.95	$62.95	$63.00
Purchase #4	$141.92	8.604%	$154.1308	$154.13	$154.15	$154.10
Purchase #5	$215.49	8.151%	$233.0546	$233.05	$233.05	$233.10
Purchase #6	$48.83	4.293%	$50.9263	$50.93	$50.95	$50.90
Purchase #7	$106.35	6.191%	$112.9341	$112.93	$112.95	$112.90
7 purchase totals =	$901.53		$979.4767	$979.47	$979.50	$979.50