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	$152.45	13.390%	$172.8631	$172.86	$172.85	$172.90
Purchase #2	$13.92	5.488%	$14.6839	$14.68	$14.70	$14.70
Purchase #3	$145.32	6.830%	$155.2454	$155.25	$155.25	$155.20
Purchase #4	$96.64	13.734%	$109.9125	$109.91	$109.90	$109.90
Purchase #5	$117.86	12.565%	$132.6691	$132.67	$132.65	$132.70
Purchase #6	$156.59	9.749%	$171.856	$171.86	$171.85	$171.90
Purchase #7	$30.65	12.214%	$34.3936	$34.39	$34.40	$34.40
7 purchase totals =	$713.43		$791.6236	$791.62	$791.60	$791.70