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	$23.29	3.475%	$24.0993	$24.10	$24.10	$24.10
Purchase #2	$32.60	5.252%	$34.3122	$34.31	$34.30	$34.30
Purchase #3	$107.61	6.406%	$114.5035	$114.50	$114.50	$114.50
Purchase #4	$247.46	13.205%	$280.1371	$280.14	$280.15	$280.10
Purchase #5	$109.34	4.684%	$114.4615	$114.46	$114.45	$114.50
Purchase #6	$125.52	4.786%	$131.5274	$131.53	$131.55	$131.50
Purchase #7	$59.78	4.545%	$62.497	$62.50	$62.50	$62.50
7 purchase totals =	$705.60		$761.5380	$761.54	$761.55	$761.50