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	$7.95	11.229%	$8.8427	$8.84	$8.85	$8.80
Purchase #2	$73.82	13.109%	$83.4971	$83.50	$83.50	$83.50
Purchase #3	$87.78	12.584%	$98.8262	$98.83	$98.85	$98.80
Purchase #4	$71.43	3.486%	$73.92	$73.92	$73.90	$73.90
Purchase #5	$59.82	10.580%	$66.149	$66.15	$66.15	$66.10
Purchase #6	$135.54	5.376%	$142.8266	$142.83	$142.85	$142.80
Purchase #7	$37.27	4.120%	$38.8055	$38.81	$38.80	$38.80
7 purchase totals =	$473.61		$512.8671	$512.88	$512.90	$512.70