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	$111.55	8.155%	$120.6469	$120.65	$120.65	$120.60
Purchase #2	$182.82	7.713%	$196.9209	$196.92	$196.90	$196.90
Purchase #3	$13.85	12.283%	$15.5512	$15.55	$15.55	$15.60
Purchase #4	$122.63	5.492%	$129.3648	$129.36	$129.35	$129.40
Purchase #5	$40.78	6.637%	$43.4866	$43.49	$43.50	$43.50
Purchase #6	$210.89	3.494%	$218.2585	$218.26	$218.25	$218.30
Purchase #7	$59.73	6.301%	$63.4936	$63.49	$63.50	$63.50
7 purchase totals =	$742.25		$787.7225	$787.72	$787.70	$787.80