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	$47.27	9.706%	$51.858	$51.86	$51.85	$51.90
Purchase #2	$9.25	11.748%	$10.3367	$10.34	$10.35	$10.30
Purchase #3	$99.53	3.305%	$102.8195	$102.82	$102.80	$102.80
Purchase #4	$41.40	13.308%	$46.9095	$46.91	$46.90	$46.90
Purchase #5	$98.71	6.380%	$105.0077	$105.01	$105.00	$105.00
Purchase #6	$97.27	7.107%	$104.183	$104.18	$104.20	$104.20
Purchase #7	$117.75	12.491%	$132.4582	$132.46	$132.45	$132.50
7 purchase totals =	$511.18		$553.5726	$553.58	$553.55	$553.60