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	$116.27	13.655%	$132.1467	$132.15	$132.15	$132.10
Purchase #2	$17.46	9.207%	$19.0675	$19.07	$19.05	$19.10
Purchase #3	$163.80	7.763%	$176.5158	$176.52	$176.50	$176.50
Purchase #4	$64.41	12.267%	$72.3112	$72.31	$72.30	$72.30
Purchase #5	$172.40	10.797%	$191.014	$191.01	$191.00	$191.00
Purchase #6	$123.38	10.788%	$136.6902	$136.69	$136.70	$136.70
Purchase #7	$65.46	11.396%	$72.9198	$72.92	$72.90	$72.90
7 purchase totals =	$723.18		$800.6652	$800.67	$800.60	$800.60