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	$208.30	9.392%	$227.8635	$227.86	$227.85	$227.90
Purchase #2	$100.50	11.511%	$112.0686	$112.07	$112.05	$112.10
Purchase #3	$214.72	12.485%	$241.5278	$241.53	$241.55	$241.50
Purchase #4	$28.68	11.558%	$31.9948	$31.99	$32.00	$32.00
Purchase #5	$98.37	5.838%	$104.1128	$104.11	$104.10	$104.10
Purchase #6	$137.57	10.794%	$152.4193	$152.42	$152.40	$152.40
Purchase #7	$204.76	4.754%	$214.4943	$214.49	$214.50	$214.50
7 purchase totals =	$992.90		$1,084.4811	$1,084.47	$1,084.45	$1,084.50