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	$100.95	8.614%	$109.6458	$109.65	$109.65	$109.60
Purchase #2	$82.79	4.300%	$86.35	$86.35	$86.35	$86.40
Purchase #3	$123.35	6.754%	$131.6811	$131.68	$131.70	$131.70
Purchase #4	$197.61	13.733%	$224.7478	$224.75	$224.75	$224.70
Purchase #5	$131.62	9.735%	$144.4332	$144.43	$144.45	$144.40
Purchase #6	$125.53	9.354%	$137.2721	$137.27	$137.25	$137.30
Purchase #7	$173.98	9.672%	$190.8073	$190.81	$190.80	$190.80
7 purchase totals =	$935.83		$1,024.9373	$1,024.94	$1,024.95	$1,024.90