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	$105.45	3.687%	$109.3379	$109.34	$109.35	$109.30
Purchase #2	$145.93	5.772%	$154.3531	$154.35	$154.35	$154.40
Purchase #3	$130.42	8.561%	$141.5853	$141.59	$141.60	$141.60
Purchase #4	$155.25	5.211%	$163.3401	$163.34	$163.35	$163.30
Purchase #5	$208.29	10.838%	$230.8645	$230.86	$230.85	$230.90
Purchase #6	$72.35	8.531%	$78.5222	$78.52	$78.50	$78.50
Purchase #7	$164.80	13.512%	$187.0678	$187.07	$187.05	$187.10
7 purchase totals =	$982.49		$1,065.0709	$1,065.07	$1,065.05	$1,065.10