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	$117.49	4.750%	$123.0708	$123.07	$123.05	$123.10
Purchase #2	$160.42	3.564%	$166.1374	$166.14	$166.15	$166.10
Purchase #3	$13.72	10.206%	$15.1203	$15.12	$15.10	$15.10
Purchase #4	$78.90	9.452%	$86.3576	$86.36	$86.35	$86.40
Purchase #5	$227.58	8.233%	$246.3167	$246.32	$246.30	$246.30
Purchase #6	$12.90	3.190%	$13.3115	$13.31	$13.30	$13.30
Purchase #7	$33.42	10.815%	$37.0344	$37.03	$37.05	$37.00
7 purchase totals =	$644.43		$687.3487	$687.35	$687.30	$687.30