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	$216.37	7.500%	$232.5978	$232.60	$232.60	$232.60
Purchase #2	$173.82	5.789%	$183.8824	$183.88	$183.90	$183.90
Purchase #3	$98.28	11.343%	$109.4279	$109.43	$109.45	$109.40
Purchase #4	$134.69	11.602%	$150.3167	$150.32	$150.30	$150.30
Purchase #5	$197.65	10.260%	$217.9289	$217.93	$217.95	$217.90
Purchase #6	$63.48	13.619%	$72.1253	$72.13	$72.15	$72.10
Purchase #7	$20.89	3.300%	$21.5794	$21.58	$21.60	$21.60
7 purchase totals =	$905.18		$987.8584	$987.87	$987.95	$987.80