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	$41.52	5.558%	$43.8277	$43.83	$43.85	$43.80
Purchase #2	$22.87	3.663%	$23.7077	$23.71	$23.70	$23.70
Purchase #3	$184.79	8.528%	$200.5489	$200.55	$200.55	$200.50
Purchase #4	$52.90	12.219%	$59.3639	$59.36	$59.35	$59.40
Purchase #5	$240.59	13.673%	$273.4859	$273.49	$273.50	$273.50
Purchase #6	$226.45	12.804%	$255.4447	$255.44	$255.45	$255.40
Purchase #7	$121.40	5.558%	$128.1474	$128.15	$128.15	$128.10
7 purchase totals =	$890.52		$984.5262	$984.53	$984.55	$984.40