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	$150.82	4.197%	$157.1499	$157.15	$157.15	$157.10
Purchase #2	$34.95	4.493%	$36.5203	$36.52	$36.50	$36.50
Purchase #3	$13.61	12.595%	$15.3242	$15.32	$15.30	$15.30
Purchase #4	$44.87	6.358%	$47.7228	$47.72	$47.70	$47.70
Purchase #5	$85.83	5.523%	$90.5704	$90.57	$90.55	$90.60
Purchase #6	$121.57	12.345%	$136.5778	$136.58	$136.60	$136.60
Purchase #7	$162.64	10.476%	$179.6782	$179.68	$179.70	$179.70
7 purchase totals =	$614.29		$663.5436	$663.54	$663.50	$663.50