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	$208.30	9.194%	$227.4511	$227.45	$227.45	$227.50
Purchase #2	$190.88	5.180%	$200.7676	$200.77	$200.75	$200.80
Purchase #3	$128.79	7.870%	$138.9258	$138.93	$138.95	$138.90
Purchase #4	$154.51	9.121%	$168.6029	$168.60	$168.60	$168.60
Purchase #5	$245.43	5.659%	$259.3189	$259.32	$259.30	$259.30
Purchase #6	$246.37	10.608%	$272.5049	$272.50	$272.50	$272.50
Purchase #7	$88.48	3.369%	$91.4609	$91.46	$91.45	$91.50
7 purchase totals =	$1,262.76		$1,359.0321	$1,359.03	$1,359.00	$1,359.10