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	$110.92	6.762%	$118.4204	$118.42	$118.40	$118.40
Purchase #2	$148.85	12.124%	$166.8966	$166.90	$166.90	$166.90
Purchase #3	$132.50	6.638%	$141.2954	$141.30	$141.30	$141.30
Purchase #4	$47.32	10.714%	$52.3899	$52.39	$52.40	$52.40
Purchase #5	$210.73	12.114%	$236.2578	$236.26	$236.25	$236.30
Purchase #6	$127.39	13.433%	$144.5023	$144.50	$144.50	$144.50
Purchase #7	$112.77	3.577%	$116.8038	$116.80	$116.80	$116.80
7 purchase totals =	$890.48		$976.5662	$976.57	$976.55	$976.60