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	$213.77	9.396%	$233.8558	$233.86	$233.85	$233.90
Purchase #2	$81.66	4.836%	$85.6091	$85.61	$85.60	$85.60
Purchase #3	$62.81	13.355%	$71.1983	$71.20	$71.20	$71.20
Purchase #4	$7.94	6.513%	$8.4571	$8.46	$8.45	$8.50
Purchase #5	$144.72	4.126%	$150.6911	$150.69	$150.70	$150.70
Purchase #6	$136.25	4.693%	$142.6442	$142.64	$142.65	$142.60
Purchase #7	$16.93	12.214%	$18.9978	$19.00	$19.00	$19.00
7 purchase totals =	$664.08		$711.4534	$711.46	$711.45	$711.50