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	$217.68	7.210%	$233.3747	$233.37	$233.35	$233.40
Purchase #2	$135.35	11.242%	$150.566	$150.57	$150.55	$150.60
Purchase #3	$191.84	4.770%	$200.9908	$200.99	$201.00	$201.00
Purchase #4	$42.98	10.357%	$47.4314	$47.43	$47.45	$47.40
Purchase #5	$148.94	11.439%	$165.9772	$165.98	$166.00	$166.00
Purchase #6	$29.80	12.464%	$33.5143	$33.51	$33.50	$33.50
Purchase #7	$178.45	3.732%	$185.1098	$185.11	$185.10	$185.10
7 purchase totals =	$945.04		$1,016.9642	$1,016.96	$1,016.95	$1,017.00