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	$39.54	8.384%	$42.855	$42.86	$42.85	$42.90
Purchase #2	$54.55	8.497%	$59.1851	$59.19	$59.20	$59.20
Purchase #3	$17.94	11.651%	$20.0302	$20.03	$20.05	$20.00
Purchase #4	$94.53	6.418%	$100.5969	$100.60	$100.60	$100.60
Purchase #5	$57.64	5.450%	$60.7814	$60.78	$60.80	$60.80
Purchase #6	$62.87	6.577%	$67.005	$67.01	$67.00	$67.00
Purchase #7	$236.49	8.588%	$256.7998	$256.80	$256.80	$256.80
7 purchase totals =	$563.56		$607.2534	$607.27	$607.30	$607.30