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	$66.48	11.395%	$74.0554	$74.06	$74.05	$74.10
Purchase #2	$111.37	11.771%	$124.4794	$124.48	$124.50	$124.50
Purchase #3	$47.30	12.414%	$53.1718	$53.17	$53.15	$53.20
Purchase #4	$7.41	6.828%	$7.916	$7.92	$7.90	$7.90
Purchase #5	$247.43	13.189%	$280.0635	$280.06	$280.05	$280.10
Purchase #6	$39.91	6.478%	$42.4954	$42.50	$42.50	$42.50
Purchase #7	$90.62	10.601%	$100.2266	$100.23	$100.25	$100.20
7 purchase totals =	$610.52		$682.4081	$682.42	$682.40	$682.50