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	$130.93	13.467%	$148.5623	$148.56	$148.55	$148.60
Purchase #2	$15.79	8.235%	$17.0903	$17.09	$17.10	$17.10
Purchase #3	$111.56	10.696%	$123.4925	$123.49	$123.50	$123.50
Purchase #4	$216.29	9.132%	$236.0416	$236.04	$236.05	$236.00
Purchase #5	$63.39	12.208%	$71.1287	$71.13	$71.15	$71.10
Purchase #6	$184.87	6.370%	$196.6462	$196.65	$196.65	$196.60
Purchase #7	$110.59	5.815%	$117.0208	$117.02	$117.00	$117.00
7 purchase totals =	$833.42		$909.9824	$909.98	$910.00	$909.90