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	$85.70	10.531%	$94.7251	$94.73	$94.75	$94.70
Purchase #2	$184.92	12.726%	$208.4529	$208.45	$208.45	$208.50
Purchase #3	$167.65	5.404%	$176.7098	$176.71	$176.70	$176.70
Purchase #4	$9.95	13.139%	$11.2573	$11.26	$11.25	$11.30
Purchase #5	$75.89	3.697%	$78.6957	$78.70	$78.70	$78.70
Purchase #6	$41.53	7.214%	$44.526	$44.53	$44.55	$44.50
Purchase #7	$189.63	5.735%	$200.5053	$200.51	$200.50	$200.50
7 purchase totals =	$755.27		$814.8721	$814.89	$814.90	$814.90