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	$225.93	6.434%	$240.4663	$240.47	$240.45	$240.50
Purchase #2	$172.99	9.477%	$189.3843	$189.38	$189.40	$189.40
Purchase #3	$174.78	4.370%	$182.4179	$182.42	$182.40	$182.40
Purchase #4	$177.59	12.326%	$199.4797	$199.48	$199.50	$199.50
Purchase #5	$169.30	3.533%	$175.2814	$175.28	$175.30	$175.30
Purchase #6	$179.38	6.382%	$190.828	$190.83	$190.85	$190.80
Purchase #7	$230.88	11.249%	$256.8517	$256.85	$256.85	$256.90
7 purchase totals =	$1,330.85		$1,434.7093	$1,434.71	$1,434.75	$1,434.80