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	$54.43	8.115%	$58.847	$58.85	$58.85	$58.80
Purchase #2	$40.85	4.415%	$42.6535	$42.65	$42.65	$42.70
Purchase #3	$14.81	11.162%	$16.4631	$16.46	$16.45	$16.50
Purchase #4	$67.72	11.429%	$75.4597	$75.46	$75.45	$75.50
Purchase #5	$117.90	8.523%	$127.9486	$127.95	$127.95	$127.90
Purchase #6	$42.97	10.628%	$47.5369	$47.54	$47.55	$47.50
Purchase #7	$65.82	10.653%	$72.8318	$72.83	$72.85	$72.80
7 purchase totals =	$404.50		$441.7406	$441.74	$441.75	$441.70