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	$151.66	5.806%	$160.4654	$160.47	$160.45	$160.50
Purchase #2	$32.83	12.286%	$36.8635	$36.86	$36.85	$36.90
Purchase #3	$98.54	6.456%	$104.9017	$104.90	$104.90	$104.90
Purchase #4	$243.28	3.550%	$251.9164	$251.92	$251.90	$251.90
Purchase #5	$149.86	4.682%	$156.8764	$156.88	$156.90	$156.90
Purchase #6	$92.56	11.139%	$102.8703	$102.87	$102.85	$102.90
Purchase #7	$95.79	8.258%	$103.7003	$103.70	$103.70	$103.70
7 purchase totals =	$864.52		$917.5940	$917.60	$917.55	$917.70