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	$246.84	7.789%	$266.0664	$266.07	$266.05	$266.10
Purchase #2	$77.52	3.536%	$80.2611	$80.26	$80.25	$80.30
Purchase #3	$62.86	8.125%	$67.9674	$67.97	$67.95	$68.00
Purchase #4	$79.32	13.501%	$90.029	$90.03	$90.05	$90.00
Purchase #5	$190.46	3.287%	$196.7204	$196.72	$196.70	$196.70
Purchase #6	$51.32	12.814%	$57.8961	$57.90	$57.90	$57.90
Purchase #7	$186.35	6.697%	$198.8299	$198.83	$198.85	$198.80
7 purchase totals =	$894.67		$957.7703	$957.78	$957.75	$957.80