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	$118.25	13.692%	$134.4408	$134.44	$134.45	$134.40
Purchase #2	$129.96	5.720%	$137.3937	$137.39	$137.40	$137.40
Purchase #3	$217.45	11.713%	$242.9199	$242.92	$242.90	$242.90
Purchase #4	$153.57	8.481%	$166.5943	$166.59	$166.60	$166.60
Purchase #5	$18.45	8.657%	$20.0472	$20.05	$20.05	$20.00
Purchase #6	$48.66	3.559%	$50.3918	$50.39	$50.40	$50.40
Purchase #7	$63.93	13.358%	$72.4698	$72.47	$72.45	$72.50
7 purchase totals =	$750.27		$824.2575	$824.25	$824.25	$824.20