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	$197.72	9.769%	$217.0353	$217.04	$217.05	$217.00
Purchase #2	$130.68	6.187%	$138.7652	$138.77	$138.75	$138.80
Purchase #3	$83.46	8.559%	$90.6033	$90.60	$90.60	$90.60
Purchase #4	$136.47	7.164%	$146.2467	$146.25	$146.25	$146.20
Purchase #5	$213.70	11.774%	$238.861	$238.86	$238.85	$238.90
Purchase #6	$30.37	3.545%	$31.4466	$31.45	$31.45	$31.40
Purchase #7	$138.99	6.697%	$148.2982	$148.30	$148.30	$148.30
7 purchase totals =	$931.39		$1,011.2563	$1,011.27	$1,011.25	$1,011.20