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	$68.70	10.638%	$76.0083	$76.01	$76.00	$76.00
Purchase #2	$46.37	4.795%	$48.5934	$48.59	$48.60	$48.60
Purchase #3	$82.75	12.791%	$93.3346	$93.33	$93.35	$93.30
Purchase #4	$67.37	4.536%	$70.4259	$70.43	$70.45	$70.40
Purchase #5	$215.34	10.808%	$238.6139	$238.61	$238.60	$238.60
Purchase #6	$68.60	7.207%	$73.544	$73.54	$73.55	$73.50
Purchase #7	$28.37	12.165%	$31.8212	$31.82	$31.80	$31.80
7 purchase totals =	$577.50		$632.3413	$632.33	$632.35	$632.20