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	$85.34	13.642%	$96.9821	$96.98	$97.00	$97.00
Purchase #2	$129.94	10.774%	$143.9397	$143.94	$143.95	$143.90
Purchase #3	$219.86	12.450%	$247.2326	$247.23	$247.25	$247.20
Purchase #4	$87.66	3.262%	$90.5195	$90.52	$90.50	$90.50
Purchase #5	$45.85	11.524%	$51.1338	$51.13	$51.15	$51.10
Purchase #6	$198.28	8.669%	$215.4689	$215.47	$215.45	$215.50
Purchase #7	$250.34	4.584%	$261.8156	$261.82	$261.80	$261.80
7 purchase totals =	$1,017.27		$1,107.0922	$1,107.09	$1,107.10	$1,107.00