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	$104.53	8.655%	$113.5771	$113.58	$113.60	$113.60
Purchase #2	$48.72	6.687%	$51.9779	$51.98	$52.00	$52.00
Purchase #3	$127.64	10.146%	$140.5904	$140.59	$140.60	$140.60
Purchase #4	$215.28	11.738%	$240.5496	$240.55	$240.55	$240.50
Purchase #5	$223.83	3.692%	$232.0938	$232.09	$232.10	$232.10
Purchase #6	$246.56	13.581%	$280.0453	$280.05	$280.05	$280.00
Purchase #7	$156.64	10.298%	$172.7708	$172.77	$172.75	$172.80
7 purchase totals =	$1,123.20		$1,231.6049	$1,231.61	$1,231.65	$1,231.60