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	$176.44	8.131%	$190.7863	$190.79	$190.80	$190.80
Purchase #2	$159.59	6.334%	$169.6984	$169.70	$169.70	$169.70
Purchase #3	$65.77	8.467%	$71.3387	$71.34	$71.35	$71.30
Purchase #4	$125.61	9.714%	$137.8118	$137.81	$137.80	$137.80
Purchase #5	$102.53	13.299%	$116.1655	$116.17	$116.15	$116.20
Purchase #6	$249.63	12.384%	$280.5442	$280.54	$280.55	$280.50
Purchase #7	$128.30	3.505%	$132.7969	$132.80	$132.80	$132.80
7 purchase totals =	$1,007.87		$1,099.1418	$1,099.15	$1,099.15	$1,099.10