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	$57.89	6.280%	$61.5255	$61.53	$61.55	$61.50
Purchase #2	$98.94	9.859%	$108.6945	$108.69	$108.70	$108.70
Purchase #3	$63.64	13.347%	$72.134	$72.13	$72.15	$72.10
Purchase #4	$131.79	3.655%	$136.6069	$136.61	$136.60	$136.60
Purchase #5	$11.54	13.322%	$13.0774	$13.08	$13.10	$13.10
Purchase #6	$121.98	7.152%	$130.704	$130.70	$130.70	$130.70
Purchase #7	$48.95	6.413%	$52.0892	$52.09	$52.10	$52.10
7 purchase totals =	$534.73		$574.8315	$574.83	$574.90	$574.80