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	$170.43	4.665%	$178.3806	$178.38	$178.40	$178.40
Purchase #2	$47.77	10.117%	$52.6029	$52.60	$52.60	$52.60
Purchase #3	$52.44	10.267%	$57.824	$57.82	$57.80	$57.80
Purchase #4	$16.26	10.330%	$17.9397	$17.94	$17.95	$17.90
Purchase #5	$89.34	12.358%	$100.3806	$100.38	$100.40	$100.40
Purchase #6	$80.43	5.778%	$85.0772	$85.08	$85.10	$85.10
Purchase #7	$190.92	10.241%	$210.4721	$210.47	$210.45	$210.50
7 purchase totals =	$647.59		$702.6771	$702.67	$702.70	$702.70