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	$136.77	4.500%	$142.9247	$142.92	$142.90	$142.90
Purchase #2	$8.77	12.508%	$9.867	$9.87	$9.85	$9.90
Purchase #3	$180.98	3.608%	$187.5098	$187.51	$187.50	$187.50
Purchase #4	$92.62	5.154%	$97.3936	$97.39	$97.40	$97.40
Purchase #5	$171.68	9.139%	$187.3698	$187.37	$187.35	$187.40
Purchase #6	$34.86	7.491%	$37.4714	$37.47	$37.45	$37.50
Purchase #7	$47.48	12.435%	$53.3841	$53.38	$53.40	$53.40
7 purchase totals =	$673.16		$715.9204	$715.91	$715.85	$716.00