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	$199.82	11.140%	$222.0799	$222.08	$222.10	$222.10
Purchase #2	$37.83	9.811%	$41.5415	$41.54	$41.55	$41.50
Purchase #3	$13.85	6.131%	$14.6991	$14.70	$14.70	$14.70
Purchase #4	$214.81	5.543%	$226.7169	$226.72	$226.70	$226.70
Purchase #5	$176.89	11.140%	$196.5955	$196.60	$196.60	$196.60
Purchase #6	$12.82	13.360%	$14.5328	$14.53	$14.55	$14.50
Purchase #7	$169.75	8.323%	$183.8783	$183.88	$183.90	$183.90
7 purchase totals =	$825.77		$900.0440	$900.05	$900.10	$900.00