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	$70.55	3.808%	$73.2365	$73.24	$73.25	$73.20
Purchase #2	$117.85	12.775%	$132.9053	$132.91	$132.90	$132.90
Purchase #3	$215.29	12.227%	$241.6135	$241.61	$241.60	$241.60
Purchase #4	$100.42	4.766%	$105.206	$105.21	$105.20	$105.20
Purchase #5	$246.96	12.783%	$278.5289	$278.53	$278.55	$278.50
Purchase #6	$43.47	5.739%	$45.9647	$45.96	$45.95	$46.00
Purchase #7	$61.69	3.737%	$63.9954	$64.00	$64.00	$64.00
7 purchase totals =	$856.23		$941.4503	$941.46	$941.45	$941.40