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	$116.82	13.670%	$132.7893	$132.79	$132.80	$132.80
Purchase #2	$196.76	13.874%	$224.0585	$224.06	$224.05	$224.10
Purchase #3	$168.69	7.648%	$181.5914	$181.59	$181.60	$181.60
Purchase #4	$68.89	5.523%	$72.6948	$72.69	$72.70	$72.70
Purchase #5	$109.27	12.237%	$122.6414	$122.64	$122.65	$122.60
Purchase #6	$116.45	10.679%	$128.8857	$128.89	$128.90	$128.90
Purchase #7	$47.61	7.817%	$51.3317	$51.33	$51.35	$51.30
7 purchase totals =	$824.49		$913.9928	$913.99	$914.05	$914.00