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	$10.44	9.502%	$11.432	$11.43	$11.45	$11.40
Purchase #2	$87.57	3.367%	$90.5185	$90.52	$90.50	$90.50
Purchase #3	$198.51	13.716%	$225.7376	$225.74	$225.75	$225.70
Purchase #4	$140.76	3.198%	$145.2615	$145.26	$145.25	$145.30
Purchase #5	$165.51	12.347%	$185.9455	$185.95	$185.95	$185.90
Purchase #6	$148.77	3.104%	$153.3878	$153.39	$153.40	$153.40
Purchase #7	$217.37	13.442%	$246.5889	$246.59	$246.60	$246.60
7 purchase totals =	$968.93		$1,058.8718	$1,058.88	$1,058.90	$1,058.80