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	$40.99	12.133%	$45.9633	$45.96	$45.95	$46.00
Purchase #2	$220.29	9.599%	$241.4356	$241.44	$241.45	$241.40
Purchase #3	$146.86	12.678%	$165.4789	$165.48	$165.50	$165.50
Purchase #4	$62.43	4.239%	$65.0764	$65.08	$65.10	$65.10
Purchase #5	$182.70	8.632%	$198.4707	$198.47	$198.45	$198.50
Purchase #6	$118.31	7.710%	$127.4317	$127.43	$127.45	$127.40
Purchase #7	$46.31	10.587%	$51.2128	$51.21	$51.20	$51.20
7 purchase totals =	$817.89		$895.0694	$895.07	$895.10	$895.10