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	$33.74	6.334%	$35.8771	$35.88	$35.90	$35.90
Purchase #2	$38.37	13.396%	$43.51	$43.51	$43.50	$43.50
Purchase #3	$221.95	11.116%	$246.622	$246.62	$246.60	$246.60
Purchase #4	$91.99	9.184%	$100.4384	$100.44	$100.45	$100.40
Purchase #5	$241.66	3.558%	$250.2583	$250.26	$250.25	$250.30
Purchase #6	$12.81	4.623%	$13.4022	$13.40	$13.40	$13.40
Purchase #7	$127.31	11.720%	$142.2307	$142.23	$142.25	$142.20
7 purchase totals =	$767.83		$832.3387	$832.34	$832.35	$832.30