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	$153.40	7.138%	$164.3497	$164.35	$164.35	$164.30
Purchase #2	$119.59	3.659%	$123.9658	$123.97	$123.95	$124.00
Purchase #3	$52.60	13.654%	$59.782	$59.78	$59.80	$59.80
Purchase #4	$143.84	8.726%	$156.3915	$156.39	$156.40	$156.40
Purchase #5	$137.26	3.829%	$142.5157	$142.52	$142.50	$142.50
Purchase #6	$216.70	11.233%	$241.0419	$241.04	$241.05	$241.00
Purchase #7	$110.44	8.640%	$119.982	$119.98	$120.00	$120.00
7 purchase totals =	$933.83		$1,008.0286	$1,008.03	$1,008.05	$1,008.00