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	$250.77	9.365%	$274.2546	$274.25	$274.25	$274.30
Purchase #2	$73.74	5.160%	$77.545	$77.55	$77.55	$77.50
Purchase #3	$132.30	5.755%	$139.9139	$139.91	$139.90	$139.90
Purchase #4	$149.59	5.859%	$158.3545	$158.35	$158.35	$158.40
Purchase #5	$59.52	11.854%	$66.5755	$66.58	$66.60	$66.60
Purchase #6	$175.75	13.312%	$199.1458	$199.15	$199.15	$199.10
Purchase #7	$120.90	8.650%	$131.3579	$131.36	$131.35	$131.40
7 purchase totals =	$962.57		$1,047.1472	$1,047.15	$1,047.15	$1,047.20