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	$136.75	11.841%	$152.9426	$152.94	$152.95	$152.90
Purchase #2	$149.53	9.142%	$163.2	$163.20	$163.20	$163.20
Purchase #3	$97.40	7.856%	$105.0517	$105.05	$105.05	$105.10
Purchase #4	$163.90	5.250%	$172.5048	$172.50	$172.50	$172.50
Purchase #5	$24.35	13.206%	$27.5657	$27.57	$27.55	$27.60
Purchase #6	$21.61	3.748%	$22.4199	$22.42	$22.40	$22.40
Purchase #7	$45.77	13.182%	$51.8034	$51.80	$51.80	$51.80
7 purchase totals =	$639.31		$695.4881	$695.48	$695.45	$695.50