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	$42.26	13.831%	$48.105	$48.11	$48.10	$48.10
Purchase #2	$114.26	4.815%	$119.7616	$119.76	$119.75	$119.80
Purchase #3	$250.93	11.382%	$279.4909	$279.49	$279.50	$279.50
Purchase #4	$218.30	10.187%	$240.5382	$240.54	$240.55	$240.50
Purchase #5	$13.38	3.553%	$13.8554	$13.86	$13.85	$13.90
Purchase #6	$102.77	8.352%	$111.3534	$111.35	$111.35	$111.40
Purchase #7	$232.70	5.619%	$245.7754	$245.78	$245.80	$245.80
7 purchase totals =	$974.60		$1,058.8799	$1,058.89	$1,058.90	$1,059.00