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	$73.60	13.735%	$83.709	$83.71	$83.70	$83.70
Purchase #2	$58.80	5.220%	$61.8694	$61.87	$61.85	$61.90
Purchase #3	$5.32	11.373%	$5.925	$5.93	$5.95	$5.90
Purchase #4	$153.80	8.264%	$166.51	$166.51	$166.50	$166.50
Purchase #5	$17.98	9.710%	$19.7259	$19.73	$19.75	$19.70
Purchase #6	$228.30	4.637%	$238.8863	$238.89	$238.90	$238.90
Purchase #7	$95.63	8.241%	$103.5109	$103.51	$103.50	$103.50
7 purchase totals =	$633.43		$680.1365	$680.15	$680.15	$680.10