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	$135.81	7.105%	$145.4593	$145.46	$145.45	$145.50
Purchase #2	$188.78	6.188%	$200.4617	$200.46	$200.45	$200.50
Purchase #3	$55.82	12.829%	$62.9811	$62.98	$63.00	$63.00
Purchase #4	$59.94	13.458%	$68.0067	$68.01	$68.00	$68.00
Purchase #5	$150.66	9.110%	$164.3851	$164.39	$164.40	$164.40
Purchase #6	$17.89	13.191%	$20.2499	$20.25	$20.25	$20.20
Purchase #7	$5.74	12.126%	$6.436	$6.44	$6.45	$6.40
7 purchase totals =	$614.64		$667.9798	$667.99	$668.00	$668.00