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	$105.55	5.173%	$111.0101	$111.01	$111.00	$111.00
Purchase #2	$231.76	5.544%	$244.6088	$244.61	$244.60	$244.60
Purchase #3	$57.34	10.626%	$63.4329	$63.43	$63.45	$63.40
Purchase #4	$246.76	13.554%	$280.2059	$280.21	$280.20	$280.20
Purchase #5	$201.28	10.790%	$222.9981	$223.00	$223.00	$223.00
Purchase #6	$119.94	3.123%	$123.6857	$123.69	$123.70	$123.70
Purchase #7	$53.75	6.382%	$57.1803	$57.18	$57.20	$57.20
7 purchase totals =	$1,016.38		$1,103.1218	$1,103.13	$1,103.15	$1,103.10