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	$68.60	5.738%	$72.5363	$72.54	$72.55	$72.50
Purchase #2	$13.34	6.668%	$14.2295	$14.23	$14.25	$14.20
Purchase #3	$31.50	9.620%	$34.5303	$34.53	$34.55	$34.50
Purchase #4	$7.94	5.509%	$8.3774	$8.38	$8.40	$8.40
Purchase #5	$34.52	4.757%	$36.1621	$36.16	$36.15	$36.20
Purchase #6	$185.99	12.654%	$209.5252	$209.53	$209.55	$209.50
Purchase #7	$45.59	12.773%	$51.4132	$51.41	$51.40	$51.40
7 purchase totals =	$387.48		$426.7740	$426.78	$426.85	$426.70