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	$66.54	9.490%	$72.8546	$72.85	$72.85	$72.90
Purchase #2	$140.61	4.320%	$146.6844	$146.68	$146.70	$146.70
Purchase #3	$183.36	9.579%	$200.9241	$200.92	$200.90	$200.90
Purchase #4	$107.86	3.546%	$111.6847	$111.68	$111.70	$111.70
Purchase #5	$7.26	11.849%	$8.1202	$8.12	$8.10	$8.10
Purchase #6	$142.46	8.556%	$154.6489	$154.65	$154.65	$154.60
Purchase #7	$242.87	10.807%	$269.117	$269.12	$269.10	$269.10
7 purchase totals =	$890.96		$964.0339	$964.02	$964.00	$964.00