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	$100.89	10.577%	$111.5611	$111.56	$111.55	$111.60
Purchase #2	$207.63	9.293%	$226.9251	$226.93	$226.95	$226.90
Purchase #3	$74.86	10.778%	$82.9284	$82.93	$82.95	$82.90
Purchase #4	$141.68	7.809%	$152.7438	$152.74	$152.75	$152.70
Purchase #5	$235.35	5.667%	$248.6873	$248.69	$248.70	$248.70
Purchase #6	$154.83	8.816%	$168.4798	$168.48	$168.50	$168.50
Purchase #7	$35.89	5.208%	$37.7592	$37.76	$37.75	$37.80
7 purchase totals =	$951.13		$1,029.0847	$1,029.09	$1,029.15	$1,029.10