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	$97.57	4.581%	$102.0397	$102.04	$102.05	$102.00
Purchase #2	$152.47	10.131%	$167.9167	$167.92	$167.90	$167.90
Purchase #3	$246.83	13.587%	$280.3668	$280.37	$280.35	$280.40
Purchase #4	$89.64	5.482%	$94.5541	$94.55	$94.55	$94.60
Purchase #5	$246.67	7.320%	$264.7262	$264.73	$264.75	$264.70
Purchase #6	$220.72	8.846%	$240.2449	$240.24	$240.25	$240.20
Purchase #7	$111.41	13.733%	$126.7099	$126.71	$126.70	$126.70
7 purchase totals =	$1,165.31		$1,276.5583	$1,276.56	$1,276.55	$1,276.50