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	$201.53	8.175%	$218.0051	$218.01	$218.00	$218.00
Purchase #2	$82.60	7.863%	$89.0948	$89.09	$89.10	$89.10
Purchase #3	$41.31	4.209%	$43.0487	$43.05	$43.05	$43.00
Purchase #4	$40.38	13.664%	$45.8975	$45.90	$45.90	$45.90
Purchase #5	$240.96	6.457%	$256.5188	$256.52	$256.50	$256.50
Purchase #6	$89.70	10.306%	$98.9445	$98.94	$98.95	$98.90
Purchase #7	$214.28	8.661%	$232.8388	$232.84	$232.85	$232.80
7 purchase totals =	$910.76		$984.3482	$984.35	$984.35	$984.20