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	$207.75	9.860%	$228.2342	$228.23	$228.25	$228.20
Purchase #2	$31.95	4.233%	$33.3024	$33.30	$33.30	$33.30
Purchase #3	$75.81	9.316%	$82.8725	$82.87	$82.85	$82.90
Purchase #4	$166.93	6.865%	$178.3897	$178.39	$178.40	$178.40
Purchase #5	$157.83	5.750%	$166.9052	$166.91	$166.90	$166.90
Purchase #6	$48.83	8.295%	$52.8804	$52.88	$52.90	$52.90
Purchase #7	$112.77	11.681%	$125.9427	$125.94	$125.95	$125.90
7 purchase totals =	$801.87		$868.5271	$868.52	$868.55	$868.50