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	$199.47	4.554%	$208.5539	$208.55	$208.55	$208.60
Purchase #2	$67.30	8.402%	$72.9545	$72.95	$72.95	$73.00
Purchase #3	$133.80	5.460%	$141.1055	$141.11	$141.10	$141.10
Purchase #4	$184.83	11.396%	$205.8932	$205.89	$205.90	$205.90
Purchase #5	$61.98	12.127%	$69.4963	$69.50	$69.50	$69.50
Purchase #6	$140.62	11.380%	$156.6226	$156.62	$156.60	$156.60
Purchase #7	$177.75	5.734%	$187.9422	$187.94	$187.95	$187.90
7 purchase totals =	$965.75		$1,042.5682	$1,042.56	$1,042.55	$1,042.60