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	$100.61	11.330%	$112.0091	$112.01	$112.00	$112.00
Purchase #2	$165.49	4.341%	$172.6739	$172.67	$172.65	$172.70
Purchase #3	$61.41	10.703%	$67.9827	$67.98	$68.00	$68.00
Purchase #4	$22.88	9.636%	$25.0847	$25.08	$25.10	$25.10
Purchase #5	$176.90	8.377%	$191.7189	$191.72	$191.70	$191.70
Purchase #6	$17.90	13.329%	$20.2859	$20.29	$20.30	$20.30
Purchase #7	$237.64	13.549%	$269.8378	$269.84	$269.85	$269.80
7 purchase totals =	$782.83		$859.5930	$859.59	$859.60	$859.60