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	$40.49	7.458%	$43.5097	$43.51	$43.50	$43.50
Purchase #2	$39.93	4.852%	$41.8674	$41.87	$41.85	$41.90
Purchase #3	$170.91	7.558%	$183.8274	$183.83	$183.85	$183.80
Purchase #4	$226.70	5.748%	$239.7307	$239.73	$239.75	$239.70
Purchase #5	$41.27	7.571%	$44.3946	$44.39	$44.40	$44.40
Purchase #6	$41.89	13.350%	$47.4823	$47.48	$47.50	$47.50
Purchase #7	$99.51	11.659%	$111.1119	$111.11	$111.10	$111.10
7 purchase totals =	$660.70		$711.9240	$711.92	$711.95	$711.90