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	$224.26	5.410%	$236.3925	$236.39	$236.40	$236.40
Purchase #2	$21.48	12.203%	$24.1012	$24.10	$24.10	$24.10
Purchase #3	$80.97	10.435%	$89.4192	$89.42	$89.40	$89.40
Purchase #4	$151.40	3.366%	$156.4961	$156.50	$156.50	$156.50
Purchase #5	$124.47	3.149%	$128.3896	$128.39	$128.40	$128.40
Purchase #6	$63.55	12.423%	$71.4448	$71.44	$71.45	$71.40
Purchase #7	$23.32	6.434%	$24.8204	$24.82	$24.80	$24.80
7 purchase totals =	$689.45		$731.0638	$731.06	$731.05	$731.00