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	$236.54	4.191%	$246.4534	$246.45	$246.45	$246.50
Purchase #2	$61.39	4.586%	$64.2053	$64.21	$64.20	$64.20
Purchase #3	$79.39	13.273%	$89.9274	$89.93	$89.95	$89.90
Purchase #4	$80.61	12.338%	$90.5557	$90.56	$90.55	$90.60
Purchase #5	$248.97	5.175%	$261.8542	$261.85	$261.85	$261.90
Purchase #6	$157.98	11.659%	$176.3989	$176.40	$176.40	$176.40
Purchase #7	$220.52	13.636%	$250.5901	$250.59	$250.60	$250.60
7 purchase totals =	$1,085.40		$1,179.9850	$1,179.99	$1,180.00	$1,180.10