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	$241.46	7.209%	$258.8669	$258.87	$258.85	$258.90
Purchase #2	$165.97	6.577%	$176.8858	$176.89	$176.90	$176.90
Purchase #3	$55.65	7.296%	$59.7102	$59.71	$59.70	$59.70
Purchase #4	$42.85	13.189%	$48.5015	$48.50	$48.50	$48.50
Purchase #5	$170.74	5.702%	$180.4756	$180.48	$180.50	$180.50
Purchase #6	$208.42	13.302%	$236.144	$236.14	$236.15	$236.10
Purchase #7	$85.36	13.654%	$97.0151	$97.02	$97.00	$97.00
7 purchase totals =	$970.45		$1,057.5991	$1,057.61	$1,057.60	$1,057.60