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	$92.56	3.260%	$95.5775	$95.58	$95.60	$95.60
Purchase #2	$40.44	6.565%	$43.0949	$43.09	$43.10	$43.10
Purchase #3	$124.33	13.249%	$140.8025	$140.80	$140.80	$140.80
Purchase #4	$36.46	3.534%	$37.7485	$37.75	$37.75	$37.70
Purchase #5	$155.25	12.648%	$174.886	$174.89	$174.90	$174.90
Purchase #6	$41.83	13.563%	$47.5034	$47.50	$47.50	$47.50
Purchase #7	$57.49	10.660%	$63.6184	$63.62	$63.60	$63.60
7 purchase totals =	$548.36		$603.2312	$603.23	$603.25	$603.20