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	$32.39	8.186%	$35.0414	$35.04	$35.05	$35.00
Purchase #2	$167.73	6.421%	$178.4999	$178.50	$178.50	$178.50
Purchase #3	$246.95	13.733%	$280.8636	$280.86	$280.85	$280.90
Purchase #4	$122.50	10.672%	$135.5732	$135.57	$135.55	$135.60
Purchase #5	$28.90	13.632%	$32.8396	$32.84	$32.85	$32.80
Purchase #6	$229.60	13.864%	$261.4317	$261.43	$261.45	$261.40
Purchase #7	$162.94	5.841%	$172.4573	$172.46	$172.45	$172.50
7 purchase totals =	$991.01		$1,096.7067	$1,096.70	$1,096.70	$1,096.70