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	$39.84	8.438%	$43.2017	$43.20	$43.20	$43.20
Purchase #2	$148.90	3.605%	$154.2678	$154.27	$154.25	$154.30
Purchase #3	$41.50	5.831%	$43.9199	$43.92	$43.90	$43.90
Purchase #4	$144.84	7.334%	$155.4626	$155.46	$155.45	$155.50
Purchase #5	$244.81	11.635%	$273.2936	$273.29	$273.30	$273.30
Purchase #6	$143.83	4.480%	$150.2736	$150.27	$150.25	$150.30
Purchase #7	$48.28	8.584%	$52.4244	$52.42	$52.40	$52.40
7 purchase totals =	$812.00		$872.8436	$872.83	$872.75	$872.90