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	$106.83	5.315%	$112.508	$112.51	$112.50	$112.50
Purchase #2	$72.79	10.404%	$80.3631	$80.36	$80.35	$80.40
Purchase #3	$233.68	9.341%	$255.508	$255.51	$255.50	$255.50
Purchase #4	$125.77	6.741%	$134.2482	$134.25	$134.25	$134.20
Purchase #5	$211.88	4.320%	$221.0332	$221.03	$221.05	$221.00
Purchase #6	$46.57	12.462%	$52.3736	$52.37	$52.35	$52.40
Purchase #7	$11.30	4.282%	$11.7839	$11.78	$11.80	$11.80
7 purchase totals =	$808.82		$867.8180	$867.81	$867.80	$867.80