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	$64.32	6.440%	$68.4622	$68.46	$68.45	$68.50
Purchase #2	$100.76	4.246%	$105.0383	$105.04	$105.05	$105.00
Purchase #3	$77.98	3.137%	$80.4262	$80.43	$80.45	$80.40
Purchase #4	$146.41	3.769%	$151.9282	$151.93	$151.95	$151.90
Purchase #5	$154.40	8.513%	$167.5441	$167.54	$167.55	$167.50
Purchase #6	$238.73	8.504%	$259.0316	$259.03	$259.05	$259.00
Purchase #7	$242.85	9.462%	$265.8285	$265.83	$265.85	$265.80
7 purchase totals =	$1,025.45		$1,098.2591	$1,098.26	$1,098.35	$1,098.10