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	$231.43	5.351%	$243.8138	$243.81	$243.80	$243.80
Purchase #2	$52.46	10.663%	$58.0538	$58.05	$58.05	$58.10
Purchase #3	$130.94	11.423%	$145.8973	$145.90	$145.90	$145.90
Purchase #4	$40.83	6.535%	$43.4982	$43.50	$43.50	$43.50
Purchase #5	$76.60	10.778%	$84.8559	$84.86	$84.85	$84.90
Purchase #6	$93.37	7.730%	$100.5875	$100.59	$100.60	$100.60
Purchase #7	$34.30	6.493%	$36.5271	$36.53	$36.55	$36.50
7 purchase totals =	$659.93		$713.2336	$713.24	$713.25	$713.30