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	$127.45	3.480%	$131.8853	$131.89	$131.90	$131.90
Purchase #2	$217.36	13.462%	$246.621	$246.62	$246.60	$246.60
Purchase #3	$57.36	8.132%	$62.0245	$62.02	$62.00	$62.00
Purchase #4	$77.71	10.789%	$86.0941	$86.09	$86.10	$86.10
Purchase #5	$49.89	3.371%	$51.5718	$51.57	$51.55	$51.60
Purchase #6	$46.77	11.731%	$52.2566	$52.26	$52.25	$52.30
Purchase #7	$41.26	11.751%	$46.1085	$46.11	$46.10	$46.10
7 purchase totals =	$617.80		$676.5618	$676.56	$676.50	$676.60