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	$204.98	8.509%	$222.4217	$222.42	$222.40	$222.40
Purchase #2	$93.42	13.189%	$105.7412	$105.74	$105.75	$105.70
Purchase #3	$65.27	13.262%	$73.9261	$73.93	$73.95	$73.90
Purchase #4	$209.72	3.556%	$217.1776	$217.18	$217.20	$217.20
Purchase #5	$244.35	4.507%	$255.3629	$255.36	$255.35	$255.40
Purchase #6	$108.26	8.142%	$117.0745	$117.07	$117.05	$117.10
Purchase #7	$78.42	8.454%	$85.0496	$85.05	$85.05	$85.00
7 purchase totals =	$1,004.42		$1,076.7536	$1,076.75	$1,076.75	$1,076.70