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	$34.62	8.333%	$37.5049	$37.50	$37.50	$37.50
Purchase #2	$127.52	11.470%	$142.1465	$142.15	$142.15	$142.10
Purchase #3	$59.41	12.436%	$66.7982	$66.80	$66.80	$66.80
Purchase #4	$211.80	11.569%	$236.3031	$236.30	$236.30	$236.30
Purchase #5	$154.89	3.395%	$160.1485	$160.15	$160.15	$160.10
Purchase #6	$95.57	9.735%	$104.8737	$104.87	$104.85	$104.90
Purchase #7	$122.82	4.222%	$128.0055	$128.01	$128.00	$128.00
7 purchase totals =	$806.63		$875.7804	$875.78	$875.75	$875.70