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	$20.39	13.559%	$23.1547	$23.15	$23.15	$23.20
Purchase #2	$63.79	4.740%	$66.8136	$66.81	$66.80	$66.80
Purchase #3	$205.89	4.430%	$215.0109	$215.01	$215.00	$215.00
Purchase #4	$58.91	9.432%	$64.4664	$64.47	$64.45	$64.50
Purchase #5	$100.57	11.260%	$111.8942	$111.89	$111.90	$111.90
Purchase #6	$46.85	13.223%	$53.045	$53.05	$53.05	$53.00
Purchase #7	$164.67	11.826%	$184.1439	$184.14	$184.15	$184.10
7 purchase totals =	$661.07		$718.5287	$718.52	$718.50	$718.50