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	$158.54	11.648%	$177.0067	$177.01	$177.00	$177.00
Purchase #2	$208.48	7.361%	$223.8262	$223.83	$223.85	$223.80
Purchase #3	$116.27	6.532%	$123.8648	$123.86	$123.85	$123.90
Purchase #4	$39.69	12.327%	$44.5826	$44.58	$44.60	$44.60
Purchase #5	$96.40	8.574%	$104.6653	$104.67	$104.65	$104.70
Purchase #6	$73.93	5.703%	$78.1462	$78.15	$78.15	$78.10
Purchase #7	$162.85	13.533%	$184.8885	$184.89	$184.90	$184.90
7 purchase totals =	$856.16		$936.9803	$936.99	$937.00	$937.00