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	$212.87	3.138%	$219.5499	$219.55	$219.55	$219.50
Purchase #2	$51.89	5.611%	$54.8015	$54.80	$54.80	$54.80
Purchase #3	$104.98	10.651%	$116.1614	$116.16	$116.15	$116.20
Purchase #4	$16.90	8.836%	$18.3933	$18.39	$18.40	$18.40
Purchase #5	$215.66	8.286%	$233.5296	$233.53	$233.55	$233.50
Purchase #6	$74.71	11.347%	$83.1873	$83.19	$83.20	$83.20
Purchase #7	$37.66	7.791%	$40.5941	$40.59	$40.60	$40.60
7 purchase totals =	$714.67		$766.2171	$766.21	$766.25	$766.20