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	$59.64	3.294%	$61.6045	$61.60	$61.60	$61.60
Purchase #2	$171.80	13.839%	$195.5754	$195.58	$195.60	$195.60
Purchase #3	$237.81	3.787%	$246.8159	$246.82	$246.80	$246.80
Purchase #4	$20.83	5.140%	$21.9007	$21.90	$21.90	$21.90
Purchase #5	$12.96	11.580%	$14.4608	$14.46	$14.45	$14.50
Purchase #6	$11.71	11.753%	$13.0863	$13.09	$13.10	$13.10
Purchase #7	$95.56	10.340%	$105.4409	$105.44	$105.45	$105.40
7 purchase totals =	$610.31		$658.8845	$658.89	$658.90	$658.90