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	$41.40	5.318%	$43.6017	$43.60	$43.60	$43.60
Purchase #2	$236.81	8.165%	$256.1455	$256.15	$256.15	$256.10
Purchase #3	$63.62	13.506%	$72.2125	$72.21	$72.20	$72.20
Purchase #4	$84.72	3.348%	$87.5564	$87.56	$87.55	$87.60
Purchase #5	$247.89	13.319%	$280.9065	$280.91	$280.90	$280.90
Purchase #6	$70.40	3.546%	$72.8964	$72.90	$72.90	$72.90
Purchase #7	$159.42	5.818%	$168.6951	$168.70	$168.70	$168.70
7 purchase totals =	$904.26		$982.0141	$982.03	$982.00	$982.00