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	$137.47	3.439%	$142.1976	$142.20	$142.20	$142.20
Purchase #2	$17.91	10.221%	$19.7406	$19.74	$19.75	$19.70
Purchase #3	$38.64	4.856%	$40.5164	$40.52	$40.50	$40.50
Purchase #4	$209.98	4.577%	$219.5908	$219.59	$219.60	$219.60
Purchase #5	$101.50	10.349%	$112.0042	$112.00	$112.00	$112.00
Purchase #6	$81.88	8.873%	$89.1452	$89.15	$89.15	$89.10
Purchase #7	$105.94	3.403%	$109.5451	$109.55	$109.55	$109.50
7 purchase totals =	$693.32		$732.7399	$732.75	$732.75	$732.60