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	$238.81	3.533%	$247.2472	$247.25	$247.25	$247.20
Purchase #2	$112.77	5.849%	$119.3659	$119.37	$119.35	$119.40
Purchase #3	$46.72	10.865%	$51.7961	$51.80	$51.80	$51.80
Purchase #4	$137.49	4.650%	$143.8833	$143.88	$143.90	$143.90
Purchase #5	$138.80	6.863%	$148.3258	$148.33	$148.35	$148.30
Purchase #6	$49.36	13.189%	$55.8701	$55.87	$55.85	$55.90
Purchase #7	$226.77	3.414%	$234.5119	$234.51	$234.50	$234.50
7 purchase totals =	$950.72		$1,001.0003	$1,001.01	$1,001.00	$1,001.00