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	$205.43	3.438%	$212.4927	$212.49	$212.50	$212.50
Purchase #2	$77.64	5.674%	$82.0453	$82.05	$82.05	$82.00
Purchase #3	$154.42	6.672%	$164.7229	$164.72	$164.70	$164.70
Purchase #4	$231.67	10.387%	$255.7336	$255.73	$255.75	$255.70
Purchase #5	$112.33	5.120%	$118.0813	$118.08	$118.10	$118.10
Purchase #6	$192.78	10.245%	$212.5303	$212.53	$212.55	$212.50
Purchase #7	$242.36	6.642%	$258.4576	$258.46	$258.45	$258.50
7 purchase totals =	$1,216.63		$1,304.0637	$1,304.06	$1,304.10	$1,304.00