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	$172.94	13.820%	$196.8403	$196.84	$196.85	$196.80
Purchase #2	$30.39	4.832%	$31.8584	$31.86	$31.85	$31.90
Purchase #3	$94.65	13.375%	$107.3094	$107.31	$107.30	$107.30
Purchase #4	$160.80	6.632%	$171.4643	$171.46	$171.45	$171.50
Purchase #5	$42.28	9.848%	$46.4437	$46.44	$46.45	$46.40
Purchase #6	$18.95	4.410%	$19.7857	$19.79	$19.80	$19.80
Purchase #7	$160.47	13.609%	$182.3084	$182.31	$182.30	$182.30
7 purchase totals =	$680.48		$756.0102	$756.01	$756.00	$756.00