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	$65.67	10.659%	$72.6698	$72.67	$72.65	$72.70
Purchase #2	$6.69	4.537%	$6.9935	$6.99	$7.00	$7.00
Purchase #3	$176.91	4.778%	$185.3628	$185.36	$185.35	$185.40
Purchase #4	$120.86	5.558%	$127.5774	$127.58	$127.60	$127.60
Purchase #5	$66.88	8.731%	$72.7193	$72.72	$72.70	$72.70
Purchase #6	$158.32	12.795%	$178.577	$178.58	$178.60	$178.60
Purchase #7	$185.38	8.421%	$200.9908	$200.99	$201.00	$201.00
7 purchase totals =	$780.71		$844.8906	$844.89	$844.90	$845.00