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	$57.44	10.248%	$63.3265	$63.33	$63.35	$63.30
Purchase #2	$138.74	8.836%	$150.9991	$151.00	$151.00	$151.00
Purchase #3	$216.44	10.359%	$238.861	$238.86	$238.85	$238.90
Purchase #4	$218.77	3.541%	$226.5166	$226.52	$226.50	$226.50
Purchase #5	$206.86	4.209%	$215.5667	$215.57	$215.55	$215.60
Purchase #6	$236.47	9.351%	$258.5823	$258.58	$258.60	$258.60
Purchase #7	$38.59	9.514%	$42.2615	$42.26	$42.25	$42.30
7 purchase totals =	$1,113.31		$1,196.1137	$1,196.12	$1,196.10	$1,196.20