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	$123.89	12.143%	$138.934	$138.93	$138.95	$138.90
Purchase #2	$45.98	4.602%	$48.096	$48.10	$48.10	$48.10
Purchase #3	$225.70	5.372%	$237.8246	$237.82	$237.80	$237.80
Purchase #4	$227.55	4.806%	$238.4861	$238.49	$238.50	$238.50
Purchase #5	$94.83	3.778%	$98.4127	$98.41	$98.40	$98.40
Purchase #6	$82.68	8.773%	$89.9335	$89.93	$89.95	$89.90
Purchase #7	$171.60	7.265%	$184.0667	$184.07	$184.05	$184.10
7 purchase totals =	$972.23		$1,035.7536	$1,035.75	$1,035.75	$1,035.70