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	$33.72	9.448%	$36.9059	$36.91	$36.90	$36.90
Purchase #2	$16.94	10.309%	$18.6863	$18.69	$18.70	$18.70
Purchase #3	$8.41	5.484%	$8.8712	$8.87	$8.85	$8.90
Purchase #4	$64.89	11.768%	$72.5263	$72.53	$72.55	$72.50
Purchase #5	$150.47	5.437%	$158.6511	$158.65	$158.65	$158.70
Purchase #6	$139.92	11.399%	$155.8695	$155.87	$155.85	$155.90
Purchase #7	$57.66	3.197%	$59.5034	$59.50	$59.50	$59.50
7 purchase totals =	$472.01		$511.0137	$511.02	$511.00	$511.10