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	$43.47	11.229%	$48.3512	$48.35	$48.35	$48.40
Purchase #2	$231.48	13.734%	$263.2715	$263.27	$263.25	$263.30
Purchase #3	$195.99	6.400%	$208.5334	$208.53	$208.55	$208.50
Purchase #4	$93.86	10.395%	$103.6167	$103.62	$103.60	$103.60
Purchase #5	$154.63	6.491%	$164.667	$164.67	$164.65	$164.70
Purchase #6	$83.66	7.857%	$90.2332	$90.23	$90.25	$90.20
Purchase #7	$124.34	10.445%	$137.3273	$137.33	$137.35	$137.30
7 purchase totals =	$927.43		$1,016.0003	$1,016.00	$1,016.00	$1,016.00