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	$118.39	4.648%	$123.8928	$123.89	$123.90	$123.90
Purchase #2	$200.72	10.866%	$222.5302	$222.53	$222.55	$222.50
Purchase #3	$249.88	5.135%	$262.7113	$262.71	$262.70	$262.70
Purchase #4	$115.47	13.656%	$131.2386	$131.24	$131.25	$131.20
Purchase #5	$59.73	9.719%	$65.5352	$65.54	$65.55	$65.50
Purchase #6	$40.76	10.226%	$44.9281	$44.93	$44.95	$44.90
Purchase #7	$239.35	11.110%	$265.9418	$265.94	$265.95	$265.90
7 purchase totals =	$1,024.30		$1,116.7780	$1,116.78	$1,116.85	$1,116.60