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	$143.91	11.672%	$160.7072	$160.71	$160.70	$160.70
Purchase #2	$12.80	13.350%	$14.5088	$14.51	$14.50	$14.50
Purchase #3	$237.86	10.334%	$262.4405	$262.44	$262.45	$262.40
Purchase #4	$49.37	4.872%	$51.7753	$51.78	$51.80	$51.80
Purchase #5	$140.25	5.314%	$147.7029	$147.70	$147.70	$147.70
Purchase #6	$180.95	8.605%	$196.5207	$196.52	$196.50	$196.50
Purchase #7	$128.68	11.814%	$143.8823	$143.88	$143.90	$143.90
7 purchase totals =	$893.82		$977.5377	$977.54	$977.55	$977.50