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	$47.66	13.193%	$53.9478	$53.95	$53.95	$53.90
Purchase #2	$199.52	11.498%	$222.4608	$222.46	$222.45	$222.50
Purchase #3	$12.28	5.697%	$12.9796	$12.98	$13.00	$13.00
Purchase #4	$106.63	11.762%	$119.1718	$119.17	$119.15	$119.20
Purchase #5	$244.27	11.123%	$271.4402	$271.44	$271.45	$271.40
Purchase #6	$126.58	13.396%	$143.5367	$143.54	$143.55	$143.50
Purchase #7	$49.83	4.776%	$52.2099	$52.21	$52.20	$52.20
7 purchase totals =	$786.77		$875.7468	$875.75	$875.75	$875.70