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	$248.54	8.254%	$269.0545	$269.05	$269.05	$269.10
Purchase #2	$209.93	10.299%	$231.5507	$231.55	$231.55	$231.60
Purchase #3	$226.43	12.842%	$255.5081	$255.51	$255.50	$255.50
Purchase #4	$107.86	3.604%	$111.7473	$111.75	$111.75	$111.70
Purchase #5	$44.67	6.408%	$47.5325	$47.53	$47.55	$47.50
Purchase #6	$94.50	6.295%	$100.4488	$100.45	$100.45	$100.40
Purchase #7	$143.75	11.758%	$160.6521	$160.65	$160.65	$160.70
7 purchase totals =	$1,075.68		$1,176.4940	$1,176.49	$1,176.50	$1,176.50