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	$139.65	10.150%	$153.8245	$153.82	$153.80	$153.80
Purchase #2	$126.30	13.439%	$143.2735	$143.27	$143.25	$143.30
Purchase #3	$108.49	13.511%	$123.1481	$123.15	$123.15	$123.10
Purchase #4	$222.97	12.506%	$250.8546	$250.85	$250.85	$250.90
Purchase #5	$117.46	4.565%	$122.822	$122.82	$122.80	$122.80
Purchase #6	$100.52	8.827%	$109.3929	$109.39	$109.40	$109.40
Purchase #7	$100.72	5.165%	$105.9222	$105.92	$105.90	$105.90
7 purchase totals =	$916.11		$1,009.2378	$1,009.22	$1,009.15	$1,009.20