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	$12.95	6.743%	$13.8232	$13.82	$13.80	$13.80
Purchase #2	$56.69	4.154%	$59.0449	$59.04	$59.05	$59.00
Purchase #3	$139.79	8.371%	$151.4918	$151.49	$151.50	$151.50
Purchase #4	$48.95	5.165%	$51.4783	$51.48	$51.50	$51.50
Purchase #5	$223.42	10.434%	$246.7316	$246.73	$246.75	$246.70
Purchase #6	$104.97	3.571%	$108.7185	$108.72	$108.70	$108.70
Purchase #7	$138.83	11.666%	$155.0259	$155.03	$155.05	$155.00
7 purchase totals =	$725.60		$786.3142	$786.31	$786.35	$786.20