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	$76.31	13.855%	$86.8828	$86.88	$86.90	$86.90
Purchase #2	$22.42	3.236%	$23.1455	$23.15	$23.15	$23.10
Purchase #3	$225.53	5.109%	$237.0523	$237.05	$237.05	$237.10
Purchase #4	$133.38	6.598%	$142.1804	$142.18	$142.20	$142.20
Purchase #5	$62.56	7.244%	$67.0918	$67.09	$67.10	$67.10
Purchase #6	$95.27	4.792%	$99.8353	$99.84	$99.85	$99.80
Purchase #7	$215.92	6.372%	$229.6784	$229.68	$229.70	$229.70
7 purchase totals =	$831.39		$885.8665	$885.87	$885.95	$885.90