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	$136.33	12.558%	$153.4503	$153.45	$153.45	$153.50
Purchase #2	$81.89	5.349%	$86.2703	$86.27	$86.25	$86.30
Purchase #3	$40.49	6.143%	$42.9773	$42.98	$43.00	$43.00
Purchase #4	$64.72	10.116%	$71.2671	$71.27	$71.25	$71.30
Purchase #5	$28.55	8.718%	$31.039	$31.04	$31.05	$31.00
Purchase #6	$11.68	11.656%	$13.0414	$13.04	$13.05	$13.00
Purchase #7	$9.25	13.733%	$10.5203	$10.52	$10.50	$10.50
7 purchase totals =	$372.91		$408.5657	$408.57	$408.55	$408.60