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	$230.45	11.477%	$256.8987	$256.90	$256.90	$256.90
Purchase #2	$157.56	11.400%	$175.5218	$175.52	$175.50	$175.50
Purchase #3	$187.86	4.203%	$195.7558	$195.76	$195.75	$195.80
Purchase #4	$128.75	10.311%	$142.0254	$142.03	$142.05	$142.00
Purchase #5	$119.92	9.637%	$131.4767	$131.48	$131.50	$131.50
Purchase #6	$50.45	8.683%	$54.8306	$54.83	$54.85	$54.80
Purchase #7	$113.45	5.577%	$119.7771	$119.78	$119.80	$119.80
7 purchase totals =	$988.44		$1,076.2861	$1,076.30	$1,076.35	$1,076.30