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	$133.78	5.184%	$140.7152	$140.72	$140.70	$140.70
Purchase #2	$215.82	7.155%	$231.2619	$231.26	$231.25	$231.30
Purchase #3	$174.38	8.378%	$188.9896	$188.99	$189.00	$189.00
Purchase #4	$27.98	13.344%	$31.7137	$31.71	$31.70	$31.70
Purchase #5	$82.46	8.358%	$89.352	$89.35	$89.35	$89.40
Purchase #6	$178.29	12.548%	$200.6618	$200.66	$200.65	$200.70
Purchase #7	$163.96	11.509%	$182.8302	$182.83	$182.85	$182.80
7 purchase totals =	$976.67		$1,065.5244	$1,065.52	$1,065.50	$1,065.60