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	$75.35	11.380%	$83.9248	$83.92	$83.90	$83.90
Purchase #2	$205.25	9.631%	$225.0176	$225.02	$225.00	$225.00
Purchase #3	$118.47	11.225%	$131.7683	$131.77	$131.75	$131.80
Purchase #4	$140.43	12.644%	$158.186	$158.19	$158.20	$158.20
Purchase #5	$68.30	6.606%	$72.8119	$72.81	$72.80	$72.80
Purchase #6	$70.66	5.250%	$74.3697	$74.37	$74.35	$74.40
Purchase #7	$228.95	11.315%	$254.8557	$254.86	$254.85	$254.90
7 purchase totals =	$907.41		$1,000.9340	$1,000.94	$1,000.85	$1,001.00