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	$44.51	6.857%	$47.5621	$47.56	$47.55	$47.60
Purchase #2	$191.29	4.272%	$199.4619	$199.46	$199.45	$199.50
Purchase #3	$177.62	11.838%	$198.6467	$198.65	$198.65	$198.60
Purchase #4	$132.76	7.454%	$142.6559	$142.66	$142.65	$142.70
Purchase #5	$29.45	11.343%	$32.7905	$32.79	$32.80	$32.80
Purchase #6	$50.57	8.176%	$54.7046	$54.70	$54.70	$54.70
Purchase #7	$39.49	11.166%	$43.8995	$43.90	$43.90	$43.90
7 purchase totals =	$665.69		$719.7212	$719.72	$719.70	$719.80