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	$83.88	9.508%	$91.8553	$91.86	$91.85	$91.90
Purchase #2	$139.80	9.768%	$153.4557	$153.46	$153.45	$153.50
Purchase #3	$198.47	5.313%	$209.0147	$209.01	$209.00	$209.00
Purchase #4	$248.40	4.584%	$259.7867	$259.79	$259.80	$259.80
Purchase #5	$47.71	7.525%	$51.3002	$51.30	$51.30	$51.30
Purchase #6	$92.36	5.522%	$97.4601	$97.46	$97.45	$97.50
Purchase #7	$72.60	8.270%	$78.604	$78.60	$78.60	$78.60
7 purchase totals =	$883.22		$941.4767	$941.48	$941.45	$941.60