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	$82.36	11.173%	$91.5621	$91.56	$91.55	$91.60
Purchase #2	$42.35	10.831%	$46.9369	$46.94	$46.95	$46.90
Purchase #3	$150.47	11.389%	$167.607	$167.61	$167.60	$167.60
Purchase #4	$132.46	8.708%	$143.9946	$143.99	$144.00	$144.00
Purchase #5	$237.83	3.257%	$245.5761	$245.58	$245.60	$245.60
Purchase #6	$121.45	8.353%	$131.5947	$131.59	$131.60	$131.60
Purchase #7	$36.60	8.376%	$39.6656	$39.67	$39.65	$39.70
7 purchase totals =	$803.52		$866.9370	$866.94	$866.95	$867.00