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	$92.55	11.357%	$103.0609	$103.06	$103.05	$103.10
Purchase #2	$111.30	4.249%	$116.0291	$116.03	$116.05	$116.00
Purchase #3	$13.93	4.354%	$14.5365	$14.54	$14.55	$14.50
Purchase #4	$63.35	6.496%	$67.4652	$67.47	$67.45	$67.50
Purchase #5	$83.68	10.844%	$92.7543	$92.75	$92.75	$92.80
Purchase #6	$175.46	8.679%	$190.6882	$190.69	$190.70	$190.70
Purchase #7	$127.83	9.503%	$139.9777	$139.98	$140.00	$140.00
7 purchase totals =	$668.10		$724.5119	$724.52	$724.55	$724.60