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	$237.34	3.240%	$245.0298	$245.03	$245.05	$245.00
Purchase #2	$33.51	12.272%	$37.6223	$37.62	$37.60	$37.60
Purchase #3	$146.85	10.326%	$162.0137	$162.01	$162.00	$162.00
Purchase #4	$67.66	13.583%	$76.8503	$76.85	$76.85	$76.90
Purchase #5	$246.57	6.195%	$261.845	$261.85	$261.85	$261.80
Purchase #6	$12.84	9.627%	$14.0761	$14.08	$14.10	$14.10
Purchase #7	$199.54	9.596%	$218.6879	$218.69	$218.70	$218.70
7 purchase totals =	$944.31		$1,016.1251	$1,016.13	$1,016.15	$1,016.10