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	$162.62	8.754%	$176.8558	$176.86	$176.85	$176.90
Purchase #2	$25.83	4.731%	$27.052	$27.05	$27.05	$27.10
Purchase #3	$211.87	6.477%	$225.5928	$225.59	$225.60	$225.60
Purchase #4	$194.95	7.475%	$209.5225	$209.52	$209.50	$209.50
Purchase #5	$140.43	10.602%	$155.3184	$155.32	$155.30	$155.30
Purchase #6	$30.73	4.629%	$32.1525	$32.15	$32.15	$32.20
Purchase #7	$100.99	11.209%	$112.31	$112.31	$112.30	$112.30
7 purchase totals =	$867.42		$938.8040	$938.80	$938.75	$938.90