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	$142.35	11.481%	$158.6932	$158.69	$158.70	$158.70
Purchase #2	$33.95	9.572%	$37.1997	$37.20	$37.20	$37.20
Purchase #3	$17.99	11.384%	$20.038	$20.04	$20.05	$20.00
Purchase #4	$124.83	5.538%	$131.7431	$131.74	$131.75	$131.70
Purchase #5	$198.79	3.413%	$205.5747	$205.57	$205.55	$205.60
Purchase #6	$190.27	13.258%	$215.496	$215.50	$215.50	$215.50
Purchase #7	$105.50	10.298%	$116.3644	$116.36	$116.35	$116.40
7 purchase totals =	$813.68		$885.1091	$885.10	$885.10	$885.10