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	$30.28	13.546%	$34.3817	$34.38	$34.40	$34.40
Purchase #2	$165.64	12.233%	$185.9027	$185.90	$185.90	$185.90
Purchase #3	$76.83	6.283%	$81.6572	$81.66	$81.65	$81.70
Purchase #4	$210.36	3.304%	$217.3103	$217.31	$217.30	$217.30
Purchase #5	$225.82	3.312%	$233.2992	$233.30	$233.30	$233.30
Purchase #6	$41.42	9.367%	$45.2998	$45.30	$45.30	$45.30
Purchase #7	$195.35	10.126%	$215.1311	$215.13	$215.15	$215.10
7 purchase totals =	$945.70		$1,012.9820	$1,012.98	$1,013.00	$1,013.00