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	$27.47	3.523%	$28.4378	$28.44	$28.45	$28.40
Purchase #2	$203.99	6.654%	$217.5635	$217.56	$217.55	$217.60
Purchase #3	$33.61	13.862%	$38.269	$38.27	$38.25	$38.30
Purchase #4	$63.98	13.738%	$72.7696	$72.77	$72.75	$72.80
Purchase #5	$39.67	5.698%	$41.9304	$41.93	$41.95	$41.90
Purchase #6	$88.55	4.509%	$92.5427	$92.54	$92.55	$92.50
Purchase #7	$222.27	7.318%	$238.5357	$238.54	$238.55	$238.50
7 purchase totals =	$679.54		$730.0487	$730.05	$730.05	$730.00