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	$160.78	11.549%	$179.3485	$179.35	$179.35	$179.30
Purchase #2	$126.64	8.733%	$137.6995	$137.70	$137.70	$137.70
Purchase #3	$85.85	4.673%	$89.8618	$89.86	$89.85	$89.90
Purchase #4	$183.92	13.566%	$208.8706	$208.87	$208.85	$208.90
Purchase #5	$155.40	10.358%	$171.4963	$171.50	$171.50	$171.50
Purchase #6	$24.82	10.559%	$27.4407	$27.44	$27.45	$27.40
Purchase #7	$195.46	9.750%	$214.5174	$214.52	$214.50	$214.50
7 purchase totals =	$932.87		$1,029.2348	$1,029.24	$1,029.20	$1,029.20