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	$130.86	7.380%	$140.5175	$140.52	$140.50	$140.50
Purchase #2	$12.47	3.314%	$12.8833	$12.88	$12.90	$12.90
Purchase #3	$70.93	12.622%	$79.8828	$79.88	$79.90	$79.90
Purchase #4	$15.56	3.800%	$16.1513	$16.15	$16.15	$16.20
Purchase #5	$211.32	9.561%	$231.5243	$231.52	$231.50	$231.50
Purchase #6	$219.30	6.521%	$233.6006	$233.60	$233.60	$233.60
Purchase #7	$56.51	8.468%	$61.2953	$61.30	$61.30	$61.30
7 purchase totals =	$716.95		$775.8551	$775.85	$775.85	$775.90