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	$221.57	10.849%	$245.6081	$245.61	$245.60	$245.60
Purchase #2	$164.86	9.499%	$180.5201	$180.52	$180.50	$180.50
Purchase #3	$121.50	4.210%	$126.6152	$126.62	$126.60	$126.60
Purchase #4	$164.42	12.151%	$184.3987	$184.40	$184.40	$184.40
Purchase #5	$173.34	3.677%	$179.7137	$179.71	$179.70	$179.70
Purchase #6	$77.27	3.606%	$80.0564	$80.06	$80.05	$80.10
Purchase #7	$20.94	9.429%	$22.9144	$22.91	$22.90	$22.90
7 purchase totals =	$943.90		$1,019.8266	$1,019.83	$1,019.75	$1,019.80