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	$160.25	11.632%	$178.8903	$178.89	$178.90	$178.90
Purchase #2	$150.51	7.328%	$161.5394	$161.54	$161.55	$161.50
Purchase #3	$134.93	7.110%	$144.5235	$144.52	$144.50	$144.50
Purchase #4	$10.40	4.585%	$10.8768	$10.88	$10.90	$10.90
Purchase #5	$185.36	7.337%	$198.9599	$198.96	$198.95	$199.00
Purchase #6	$177.96	8.661%	$193.3731	$193.37	$193.35	$193.40
Purchase #7	$148.81	10.506%	$164.444	$164.44	$164.45	$164.40
7 purchase totals =	$968.22		$1,052.6070	$1,052.60	$1,052.60	$1,052.60