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	$146.78	7.512%	$157.8061	$157.81	$157.80	$157.80
Purchase #2	$19.77	5.459%	$20.8492	$20.85	$20.85	$20.80
Purchase #3	$63.29	13.845%	$72.0525	$72.05	$72.05	$72.10
Purchase #4	$241.59	10.107%	$266.0075	$266.01	$266.00	$266.00
Purchase #5	$185.59	8.268%	$200.9346	$200.93	$200.95	$200.90
Purchase #6	$126.89	4.389%	$132.4592	$132.46	$132.45	$132.50
Purchase #7	$246.96	10.844%	$273.7403	$273.74	$273.75	$273.70
7 purchase totals =	$1,030.87		$1,123.8494	$1,123.85	$1,123.85	$1,123.80