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	$59.69	10.156%	$65.7521	$65.75	$65.75	$65.80
Purchase #2	$142.55	11.863%	$159.4607	$159.46	$159.45	$159.50
Purchase #3	$143.86	8.487%	$156.0694	$156.07	$156.05	$156.10
Purchase #4	$59.96	12.568%	$67.4958	$67.50	$67.50	$67.50
Purchase #5	$93.42	6.436%	$99.4325	$99.43	$99.45	$99.40
Purchase #6	$134.95	13.870%	$153.6676	$153.67	$153.65	$153.70
Purchase #7	$208.99	6.583%	$222.7478	$222.75	$222.75	$222.70
7 purchase totals =	$843.42		$924.6259	$924.63	$924.60	$924.70