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	$40.63	10.298%	$44.8141	$44.81	$44.80	$44.80
Purchase #2	$46.62	9.489%	$51.0438	$51.04	$51.05	$51.00
Purchase #3	$73.66	11.850%	$82.3887	$82.39	$82.40	$82.40
Purchase #4	$36.65	4.870%	$38.4349	$38.43	$38.45	$38.40
Purchase #5	$78.78	4.628%	$82.4259	$82.43	$82.45	$82.40
Purchase #6	$10.90	10.605%	$12.0559	$12.06	$12.05	$12.10
Purchase #7	$194.42	4.858%	$203.8649	$203.86	$203.85	$203.90
7 purchase totals =	$481.66		$515.0282	$515.02	$515.05	$515.00