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	$111.38	11.743%	$124.4594	$124.46	$124.45	$124.50
Purchase #2	$223.63	4.295%	$233.2349	$233.23	$233.25	$233.20
Purchase #3	$106.87	11.783%	$119.4625	$119.46	$119.45	$119.50
Purchase #4	$138.83	3.733%	$144.0125	$144.01	$144.00	$144.00
Purchase #5	$124.96	3.109%	$128.845	$128.85	$128.85	$128.80
Purchase #6	$76.96	8.555%	$83.5439	$83.54	$83.55	$83.50
Purchase #7	$110.41	10.383%	$121.8739	$121.87	$121.85	$121.90
7 purchase totals =	$893.04		$955.4321	$955.42	$955.40	$955.40