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	$178.83	7.684%	$192.5713	$192.57	$192.55	$192.60
Purchase #2	$38.99	11.624%	$43.5222	$43.52	$43.50	$43.50
Purchase #3	$164.42	10.792%	$182.1642	$182.16	$182.15	$182.20
Purchase #4	$87.51	8.601%	$95.0367	$95.04	$95.05	$95.00
Purchase #5	$130.47	8.411%	$141.4438	$141.44	$141.45	$141.40
Purchase #6	$234.93	7.141%	$251.7064	$251.71	$251.70	$251.70
Purchase #7	$142.93	8.638%	$155.2763	$155.28	$155.30	$155.30
7 purchase totals =	$978.08		$1,061.7209	$1,061.72	$1,061.70	$1,061.70