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	$229.70	5.352%	$241.9935	$241.99	$242.00	$242.00
Purchase #2	$140.69	10.864%	$155.9746	$155.97	$155.95	$156.00
Purchase #3	$77.52	10.667%	$85.7891	$85.79	$85.80	$85.80
Purchase #4	$136.75	3.234%	$141.1725	$141.17	$141.15	$141.20
Purchase #5	$132.93	7.226%	$142.5355	$142.54	$142.55	$142.50
Purchase #6	$174.99	6.344%	$186.0914	$186.09	$186.10	$186.10
Purchase #7	$104.43	7.171%	$111.9187	$111.92	$111.90	$111.90
7 purchase totals =	$997.01		$1,065.4753	$1,065.47	$1,065.45	$1,065.50