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	$231.53	10.382%	$255.5674	$255.57	$255.55	$255.60
Purchase #2	$231.92	10.678%	$256.6844	$256.68	$256.70	$256.70
Purchase #3	$175.85	8.684%	$191.1208	$191.12	$191.10	$191.10
Purchase #4	$220.87	10.472%	$243.9995	$244.00	$244.00	$244.00
Purchase #5	$44.31	13.755%	$50.4048	$50.40	$50.40	$50.40
Purchase #6	$50.26	11.387%	$55.9831	$55.98	$56.00	$56.00
Purchase #7	$29.56	9.583%	$32.3927	$32.39	$32.40	$32.40
7 purchase totals =	$984.30		$1,086.1527	$1,086.14	$1,086.15	$1,086.20