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	$241.53	10.789%	$267.5887	$267.59	$267.60	$267.60
Purchase #2	$90.67	3.478%	$93.8235	$93.82	$93.80	$93.80
Purchase #3	$63.64	6.509%	$67.7823	$67.78	$67.80	$67.80
Purchase #4	$236.42	6.421%	$251.6005	$251.60	$251.60	$251.60
Purchase #5	$96.73	7.463%	$103.949	$103.95	$103.95	$103.90
Purchase #6	$37.31	11.406%	$41.5656	$41.57	$41.55	$41.60
Purchase #7	$134.90	12.123%	$151.2539	$151.25	$151.25	$151.30
7 purchase totals =	$901.20		$977.5635	$977.56	$977.55	$977.60