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	$221.31	13.826%	$251.9083	$251.91	$251.90	$251.90
Purchase #2	$225.58	4.546%	$235.8349	$235.83	$235.85	$235.80
Purchase #3	$101.79	10.610%	$112.5899	$112.59	$112.60	$112.60
Purchase #4	$80.51	6.208%	$85.5081	$85.51	$85.50	$85.50
Purchase #5	$109.92	12.677%	$123.8546	$123.85	$123.85	$123.90
Purchase #6	$157.52	6.795%	$168.2235	$168.22	$168.20	$168.20
Purchase #7	$73.36	8.489%	$79.5875	$79.59	$79.60	$79.60
7 purchase totals =	$969.99		$1,057.5068	$1,057.50	$1,057.50	$1,057.50