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	$61.67	13.230%	$69.8289	$69.83	$69.85	$69.80
Purchase #2	$23.52	4.561%	$24.5927	$24.59	$24.60	$24.60
Purchase #3	$170.57	8.812%	$185.6006	$185.60	$185.60	$185.60
Purchase #4	$141.71	9.620%	$155.3425	$155.34	$155.35	$155.30
Purchase #5	$162.78	9.681%	$178.5387	$178.54	$178.55	$178.50
Purchase #6	$206.91	4.302%	$215.8113	$215.81	$215.80	$215.80
Purchase #7	$224.82	13.821%	$255.8924	$255.89	$255.90	$255.90
7 purchase totals =	$991.98		$1,085.6071	$1,085.60	$1,085.65	$1,085.50