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	$137.53	13.757%	$156.45	$156.45	$156.45	$156.50
Purchase #2	$236.42	8.185%	$255.771	$255.77	$255.75	$255.80
Purchase #3	$94.80	3.724%	$98.3304	$98.33	$98.35	$98.30
Purchase #4	$142.94	8.643%	$155.2943	$155.29	$155.30	$155.30
Purchase #5	$126.56	5.590%	$133.6347	$133.63	$133.65	$133.60
Purchase #6	$129.78	10.253%	$143.0863	$143.09	$143.10	$143.10
Purchase #7	$96.59	9.258%	$105.5323	$105.53	$105.55	$105.50
7 purchase totals =	$964.62		$1,048.0990	$1,048.09	$1,048.15	$1,048.10