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	$210.66	10.868%	$233.5545	$233.55	$233.55	$233.60
Purchase #2	$50.92	9.861%	$55.9412	$55.94	$55.95	$55.90
Purchase #3	$105.38	12.529%	$118.5831	$118.58	$118.60	$118.60
Purchase #4	$71.54	8.396%	$77.5465	$77.55	$77.55	$77.50
Purchase #5	$10.61	9.260%	$11.5925	$11.59	$11.60	$11.60
Purchase #6	$123.71	11.158%	$137.5136	$137.51	$137.50	$137.50
Purchase #7	$160.61	12.660%	$180.9432	$180.94	$180.95	$180.90
7 purchase totals =	$733.43		$815.6746	$815.66	$815.70	$815.60