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	$100.52	9.381%	$109.9498	$109.95	$109.95	$109.90
Purchase #2	$140.87	9.704%	$154.54	$154.54	$154.55	$154.50
Purchase #3	$135.96	7.263%	$145.8348	$145.83	$145.85	$145.80
Purchase #4	$38.36	5.482%	$40.4629	$40.46	$40.45	$40.50
Purchase #5	$155.37	4.573%	$162.4751	$162.48	$162.50	$162.50
Purchase #6	$248.87	8.237%	$269.3694	$269.37	$269.35	$269.40
Purchase #7	$127.78	7.516%	$137.3839	$137.38	$137.40	$137.40
7 purchase totals =	$947.73		$1,020.0159	$1,020.01	$1,020.05	$1,020.00