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	$220.89	5.789%	$233.6773	$233.68	$233.70	$233.70
Purchase #2	$56.54	10.533%	$62.4954	$62.50	$62.50	$62.50
Purchase #3	$96.40	6.466%	$102.6332	$102.63	$102.65	$102.60
Purchase #4	$122.42	4.874%	$128.3868	$128.39	$128.40	$128.40
Purchase #5	$30.75	10.300%	$33.9173	$33.92	$33.90	$33.90
Purchase #6	$56.67	11.822%	$63.3695	$63.37	$63.35	$63.40
Purchase #7	$138.64	3.104%	$142.9434	$142.94	$142.95	$142.90
7 purchase totals =	$722.31		$767.4229	$767.43	$767.45	$767.40