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	$121.65	8.329%	$131.7822	$131.78	$131.80	$131.80
Purchase #2	$175.52	12.158%	$196.8597	$196.86	$196.85	$196.90
Purchase #3	$41.33	3.697%	$42.858	$42.86	$42.85	$42.90
Purchase #4	$106.89	13.150%	$120.946	$120.95	$120.95	$120.90
Purchase #5	$217.31	3.410%	$224.7203	$224.72	$224.70	$224.70
Purchase #6	$28.98	3.130%	$29.8871	$29.89	$29.90	$29.90
Purchase #7	$185.35	10.537%	$204.8803	$204.88	$204.90	$204.90
7 purchase totals =	$877.03		$951.9336	$951.94	$951.95	$952.00