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	$162.89	9.146%	$177.7879	$177.79	$177.80	$177.80
Purchase #2	$74.72	10.200%	$82.3414	$82.34	$82.35	$82.30
Purchase #3	$169.52	11.836%	$189.5844	$189.58	$189.60	$189.60
Purchase #4	$38.85	11.843%	$43.451	$43.45	$43.45	$43.50
Purchase #5	$35.43	13.618%	$40.2549	$40.25	$40.25	$40.30
Purchase #6	$49.39	6.266%	$52.4848	$52.48	$52.50	$52.50
Purchase #7	$5.63	13.590%	$6.3951	$6.40	$6.40	$6.40
7 purchase totals =	$536.43		$592.2995	$592.29	$592.35	$592.40