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	$176.51	4.478%	$184.4141	$184.41	$184.40	$184.40
Purchase #2	$114.40	7.858%	$123.3896	$123.39	$123.40	$123.40
Purchase #3	$246.50	13.830%	$280.591	$280.59	$280.60	$280.60
Purchase #4	$140.34	3.178%	$144.8	$144.80	$144.80	$144.80
Purchase #5	$102.58	5.857%	$108.5881	$108.59	$108.60	$108.60
Purchase #6	$73.33	8.786%	$79.7728	$79.77	$79.75	$79.80
Purchase #7	$169.61	10.634%	$187.6463	$187.65	$187.65	$187.60
7 purchase totals =	$1,023.27		$1,109.2019	$1,109.20	$1,109.20	$1,109.20