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	$194.85	10.229%	$214.7812	$214.78	$214.80	$214.80
Purchase #2	$148.88	12.744%	$167.8533	$167.85	$167.85	$167.90
Purchase #3	$44.39	7.826%	$47.864	$47.86	$47.85	$47.90
Purchase #4	$133.41	8.142%	$144.2722	$144.27	$144.25	$144.30
Purchase #5	$43.33	10.727%	$47.978	$47.98	$48.00	$48.00
Purchase #6	$135.55	5.245%	$142.6596	$142.66	$142.65	$142.70
Purchase #7	$200.61	13.507%	$227.7064	$227.71	$227.70	$227.70
7 purchase totals =	$901.02		$993.1147	$993.11	$993.10	$993.30