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	$217.30	7.815%	$234.282	$234.28	$234.30	$234.30
Purchase #2	$241.61	6.555%	$257.4475	$257.45	$257.45	$257.40
Purchase #3	$125.94	8.670%	$136.859	$136.86	$136.85	$136.90
Purchase #4	$105.94	5.486%	$111.7519	$111.75	$111.75	$111.80
Purchase #5	$78.69	4.845%	$82.5025	$82.50	$82.50	$82.50
Purchase #6	$101.45	7.730%	$109.2921	$109.29	$109.30	$109.30
Purchase #7	$80.91	6.126%	$85.8665	$85.87	$85.85	$85.90
7 purchase totals =	$951.84		$1,018.0015	$1,018.00	$1,018.00	$1,018.10