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	$78.80	3.492%	$81.5517	$81.55	$81.55	$81.60
Purchase #2	$85.25	3.392%	$88.1417	$88.14	$88.15	$88.10
Purchase #3	$84.32	12.665%	$94.9991	$95.00	$95.00	$95.00
Purchase #4	$213.55	6.462%	$227.3496	$227.35	$227.35	$227.30
Purchase #5	$161.67	13.297%	$183.1673	$183.17	$183.15	$183.20
Purchase #6	$20.89	3.430%	$21.6065	$21.61	$21.60	$21.60
Purchase #7	$89.39	12.479%	$100.545	$100.55	$100.55	$100.50
7 purchase totals =	$733.87		$797.3609	$797.37	$797.35	$797.30