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	$143.92	11.832%	$160.9486	$160.95	$160.95	$160.90
Purchase #2	$250.39	12.536%	$281.7789	$281.78	$281.80	$281.80
Purchase #3	$59.66	4.596%	$62.402	$62.40	$62.40	$62.40
Purchase #4	$69.60	11.626%	$77.6917	$77.69	$77.70	$77.70
Purchase #5	$85.69	4.325%	$89.3961	$89.40	$89.40	$89.40
Purchase #6	$29.75	7.218%	$31.8974	$31.90	$31.90	$31.90
Purchase #7	$60.66	4.633%	$63.4704	$63.47	$63.45	$63.50
7 purchase totals =	$699.67		$767.5851	$767.59	$767.60	$767.60