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	$176.48	12.683%	$198.863	$198.86	$198.85	$198.90
Purchase #2	$244.50	11.151%	$271.7642	$271.76	$271.75	$271.80
Purchase #3	$27.32	8.301%	$29.5878	$29.59	$29.60	$29.60
Purchase #4	$24.52	11.571%	$27.3572	$27.36	$27.35	$27.40
Purchase #5	$150.96	4.870%	$158.3118	$158.31	$158.30	$158.30
Purchase #6	$139.35	11.233%	$155.0032	$155.00	$155.00	$155.00
Purchase #7	$161.97	9.109%	$176.7238	$176.72	$176.70	$176.70
7 purchase totals =	$925.10		$1,017.6110	$1,017.60	$1,017.55	$1,017.70