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	$107.51	8.202%	$116.328	$116.33	$116.35	$116.30
Purchase #2	$31.91	6.864%	$34.1003	$34.10	$34.10	$34.10
Purchase #3	$168.81	5.726%	$178.4761	$178.48	$178.50	$178.50
Purchase #4	$134.41	6.254%	$142.816	$142.82	$142.80	$142.80
Purchase #5	$98.72	11.208%	$109.7845	$109.78	$109.80	$109.80
Purchase #6	$195.40	7.406%	$209.8713	$209.87	$209.85	$209.90
Purchase #7	$49.61	4.218%	$51.7025	$51.70	$51.70	$51.70
7 purchase totals =	$786.37		$843.0787	$843.08	$843.10	$843.10