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	$116.73	13.129%	$132.0555	$132.06	$132.05	$132.10
Purchase #2	$219.75	9.427%	$240.4658	$240.47	$240.45	$240.50
Purchase #3	$227.59	11.807%	$254.4616	$254.46	$254.45	$254.50
Purchase #4	$64.78	12.482%	$72.8658	$72.87	$72.85	$72.90
Purchase #5	$91.96	12.741%	$103.6766	$103.68	$103.70	$103.70
Purchase #6	$116.28	12.756%	$131.1127	$131.11	$131.10	$131.10
Purchase #7	$248.59	12.742%	$280.2653	$280.27	$280.25	$280.30
7 purchase totals =	$1,085.68		$1,214.9033	$1,214.92	$1,214.85	$1,215.10