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	$225.88	4.482%	$236.0039	$236.00	$236.00	$236.00
Purchase #2	$231.72	10.752%	$256.6345	$256.63	$256.65	$256.60
Purchase #3	$38.82	12.267%	$43.582	$43.58	$43.60	$43.60
Purchase #4	$205.86	5.495%	$217.172	$217.17	$217.15	$217.20
Purchase #5	$57.78	11.155%	$64.2254	$64.23	$64.25	$64.20
Purchase #6	$52.57	3.803%	$54.5692	$54.57	$54.55	$54.60
Purchase #7	$177.41	12.548%	$199.6714	$199.67	$199.65	$199.70
7 purchase totals =	$990.04		$1,071.8584	$1,071.85	$1,071.85	$1,071.90