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	$183.94	11.864%	$205.7626	$205.76	$205.75	$205.80
Purchase #2	$246.30	10.656%	$272.5457	$272.55	$272.55	$272.50
Purchase #3	$132.33	8.550%	$143.6442	$143.64	$143.65	$143.60
Purchase #4	$29.80	13.256%	$33.7503	$33.75	$33.75	$33.80
Purchase #5	$28.34	11.711%	$31.6589	$31.66	$31.65	$31.70
Purchase #6	$231.89	13.686%	$263.6265	$263.63	$263.65	$263.60
Purchase #7	$177.68	12.862%	$200.5332	$200.53	$200.55	$200.50
7 purchase totals =	$1,030.28		$1,151.5214	$1,151.52	$1,151.55	$1,151.50