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	$200.95	9.741%	$220.5245	$220.52	$220.50	$220.50
Purchase #2	$221.80	7.855%	$239.2224	$239.22	$239.20	$239.20
Purchase #3	$226.37	7.569%	$243.5039	$243.50	$243.50	$243.50
Purchase #4	$106.37	4.426%	$111.0779	$111.08	$111.10	$111.10
Purchase #5	$73.71	6.365%	$78.4016	$78.40	$78.40	$78.40
Purchase #6	$14.69	7.736%	$15.8264	$15.83	$15.85	$15.80
Purchase #7	$38.93	7.583%	$41.8821	$41.88	$41.90	$41.90
7 purchase totals =	$882.82		$950.4388	$950.43	$950.45	$950.40