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	$211.52	9.455%	$231.5192	$231.52	$231.50	$231.50
Purchase #2	$131.36	6.820%	$140.3188	$140.32	$140.30	$140.30
Purchase #3	$6.80	10.325%	$7.5021	$7.50	$7.50	$7.50
Purchase #4	$229.82	10.332%	$253.565	$253.57	$253.55	$253.60
Purchase #5	$83.48	9.725%	$91.5984	$91.60	$91.60	$91.60
Purchase #6	$246.34	10.607%	$272.4693	$272.47	$272.45	$272.50
Purchase #7	$44.48	4.622%	$46.5359	$46.54	$46.55	$46.50
7 purchase totals =	$953.80		$1,043.5087	$1,043.52	$1,043.45	$1,043.50