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	$143.89	11.725%	$160.7611	$160.76	$160.75	$160.80
Purchase #2	$85.54	11.375%	$95.2702	$95.27	$95.25	$95.30
Purchase #3	$243.40	11.504%	$271.4007	$271.40	$271.40	$271.40
Purchase #4	$39.79	7.358%	$42.7177	$42.72	$42.70	$42.70
Purchase #5	$128.43	9.603%	$140.7631	$140.76	$140.75	$140.80
Purchase #6	$116.81	8.369%	$126.5858	$126.59	$126.60	$126.60
Purchase #7	$112.85	6.727%	$120.4414	$120.44	$120.45	$120.40
7 purchase totals =	$870.71		$957.9400	$957.94	$957.90	$958.00