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	$245.75	9.654%	$269.4747	$269.47	$269.45	$269.50
Purchase #2	$9.57	9.761%	$10.5041	$10.50	$10.50	$10.50
Purchase #3	$54.83	8.328%	$59.3962	$59.40	$59.40	$59.40
Purchase #4	$149.32	7.492%	$160.5071	$160.51	$160.50	$160.50
Purchase #5	$84.70	4.775%	$88.7444	$88.74	$88.75	$88.70
Purchase #6	$157.51	8.713%	$171.2338	$171.23	$171.25	$171.20
Purchase #7	$248.92	12.566%	$280.1993	$280.20	$280.20	$280.20
7 purchase totals =	$950.60		$1,040.0596	$1,040.05	$1,040.05	$1,040.00