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	$111.71	5.864%	$118.2607	$118.26	$118.25	$118.30
Purchase #2	$90.72	8.310%	$98.2588	$98.26	$98.25	$98.30
Purchase #3	$75.58	9.792%	$82.9808	$82.98	$83.00	$83.00
Purchase #4	$34.46	7.265%	$36.9635	$36.96	$36.95	$37.00
Purchase #5	$15.88	10.815%	$17.5974	$17.60	$17.60	$17.60
Purchase #6	$163.36	13.785%	$185.8792	$185.88	$185.90	$185.90
Purchase #7	$105.83	6.677%	$112.8963	$112.90	$112.90	$112.90
7 purchase totals =	$597.54		$652.8367	$652.84	$652.85	$653.00