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	$34.51	10.248%	$38.0466	$38.05	$38.05	$38.00
Purchase #2	$83.42	13.809%	$94.9395	$94.94	$94.95	$94.90
Purchase #3	$121.81	13.874%	$138.7099	$138.71	$138.70	$138.70
Purchase #4	$247.56	13.443%	$280.8395	$280.84	$280.85	$280.80
Purchase #5	$177.57	12.372%	$199.539	$199.54	$199.55	$199.50
Purchase #6	$99.85	11.503%	$111.3357	$111.34	$111.35	$111.30
Purchase #7	$176.90	4.361%	$184.6146	$184.61	$184.60	$184.60
7 purchase totals =	$941.62		$1,048.0248	$1,048.03	$1,048.05	$1,047.80