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	$104.38	7.783%	$112.5039	$112.50	$112.50	$112.50
Purchase #2	$54.93	12.568%	$61.8336	$61.83	$61.85	$61.80
Purchase #3	$117.59	10.826%	$130.3203	$130.32	$130.30	$130.30
Purchase #4	$52.32	5.380%	$55.1348	$55.13	$55.15	$55.10
Purchase #5	$134.32	12.858%	$151.5909	$151.59	$151.60	$151.60
Purchase #6	$112.57	7.599%	$121.1242	$121.12	$121.10	$121.10
Purchase #7	$114.67	4.461%	$119.7854	$119.79	$119.80	$119.80
7 purchase totals =	$690.78		$752.2931	$752.28	$752.30	$752.20