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	$241.96	11.192%	$269.0402	$269.04	$269.05	$269.00
Purchase #2	$158.50	3.773%	$164.4802	$164.48	$164.50	$164.50
Purchase #3	$126.25	12.271%	$141.7421	$141.74	$141.75	$141.70
Purchase #4	$61.98	4.414%	$64.7158	$64.72	$64.70	$64.70
Purchase #5	$62.92	11.832%	$70.3647	$70.36	$70.35	$70.40
Purchase #6	$153.34	3.504%	$158.713	$158.71	$158.70	$158.70
Purchase #7	$161.95	5.870%	$171.4565	$171.46	$171.45	$171.50
7 purchase totals =	$966.90		$1,040.5125	$1,040.51	$1,040.50	$1,040.50