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	$206.72	5.468%	$218.0234	$218.02	$218.00	$218.00
Purchase #2	$40.35	13.725%	$45.888	$45.89	$45.90	$45.90
Purchase #3	$146.26	6.841%	$156.2656	$156.27	$156.25	$156.30
Purchase #4	$157.83	5.826%	$167.0252	$167.03	$167.05	$167.00
Purchase #5	$231.59	4.108%	$241.1037	$241.10	$241.10	$241.10
Purchase #6	$242.87	6.112%	$257.7142	$257.71	$257.70	$257.70
Purchase #7	$55.50	12.439%	$62.4036	$62.40	$62.40	$62.40
7 purchase totals =	$1,081.12		$1,148.4237	$1,148.42	$1,148.40	$1,148.40