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	$196.40	9.181%	$214.4315	$214.43	$214.45	$214.40
Purchase #2	$140.56	3.108%	$144.9286	$144.93	$144.95	$144.90
Purchase #3	$150.71	4.752%	$157.8717	$157.87	$157.85	$157.90
Purchase #4	$137.42	13.459%	$155.9154	$155.92	$155.90	$155.90
Purchase #5	$240.40	13.694%	$273.3204	$273.32	$273.30	$273.30
Purchase #6	$81.72	8.482%	$88.6515	$88.65	$88.65	$88.70
Purchase #7	$129.47	11.803%	$144.7513	$144.75	$144.75	$144.80
7 purchase totals =	$1,076.68		$1,179.8704	$1,179.87	$1,179.85	$1,179.90