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	$133.64	4.364%	$139.472	$139.47	$139.45	$139.50
Purchase #2	$63.95	12.818%	$72.1471	$72.15	$72.15	$72.10
Purchase #3	$23.25	5.382%	$24.5013	$24.50	$24.50	$24.50
Purchase #4	$46.85	5.852%	$49.5917	$49.59	$49.60	$49.60
Purchase #5	$155.52	5.126%	$163.492	$163.49	$163.50	$163.50
Purchase #6	$227.94	4.184%	$237.477	$237.48	$237.50	$237.50
Purchase #7	$66.64	8.257%	$72.1425	$72.14	$72.15	$72.10
7 purchase totals =	$717.79		$758.8236	$758.82	$758.85	$758.80