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	$238.39	9.314%	$260.5936	$260.59	$260.60	$260.60
Purchase #2	$86.35	9.192%	$94.2873	$94.29	$94.30	$94.30
Purchase #3	$128.76	9.833%	$141.421	$141.42	$141.40	$141.40
Purchase #4	$138.78	8.143%	$150.0809	$150.08	$150.10	$150.10
Purchase #5	$129.63	10.729%	$143.538	$143.54	$143.55	$143.50
Purchase #6	$135.38	13.811%	$154.0773	$154.08	$154.10	$154.10
Purchase #7	$127.62	12.727%	$143.8622	$143.86	$143.85	$143.90
7 purchase totals =	$984.91		$1,087.8603	$1,087.86	$1,087.90	$1,087.90