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	$24.93	3.208%	$25.7298	$25.73	$25.75	$25.70
Purchase #2	$204.54	10.463%	$225.941	$225.94	$225.95	$225.90
Purchase #3	$246.27	13.788%	$280.2257	$280.23	$280.25	$280.20
Purchase #4	$114.50	7.175%	$122.7154	$122.72	$122.70	$122.70
Purchase #5	$200.68	10.818%	$222.3896	$222.39	$222.40	$222.40
Purchase #6	$36.47	3.702%	$37.8201	$37.82	$37.80	$37.80
Purchase #7	$135.51	11.335%	$150.8701	$150.87	$150.85	$150.90
7 purchase totals =	$962.90		$1,065.6917	$1,065.70	$1,065.70	$1,065.60