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	$41.69	3.234%	$43.0383	$43.04	$43.05	$43.00
Purchase #2	$107.42	3.797%	$111.4987	$111.50	$111.50	$111.50
Purchase #3	$39.57	3.647%	$41.0131	$41.01	$41.00	$41.00
Purchase #4	$182.52	9.752%	$200.3194	$200.32	$200.30	$200.30
Purchase #5	$88.31	4.467%	$92.2548	$92.25	$92.25	$92.30
Purchase #6	$243.44	5.515%	$256.8657	$256.87	$256.85	$256.90
Purchase #7	$115.43	6.123%	$122.4978	$122.50	$122.50	$122.50
7 purchase totals =	$818.38		$867.4878	$867.49	$867.45	$867.50