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	$100.96	10.414%	$111.474	$111.47	$111.45	$111.50
Purchase #2	$179.37	9.546%	$196.4927	$196.49	$196.50	$196.50
Purchase #3	$35.86	9.477%	$39.2585	$39.26	$39.25	$39.30
Purchase #4	$39.99	7.504%	$42.9908	$42.99	$43.00	$43.00
Purchase #5	$91.92	11.240%	$102.2518	$102.25	$102.25	$102.30
Purchase #6	$132.55	6.261%	$140.849	$140.85	$140.85	$140.80
Purchase #7	$240.36	6.381%	$255.6974	$255.70	$255.70	$255.70
7 purchase totals =	$821.01		$889.0142	$889.01	$889.00	$889.10