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	$156.47	7.685%	$168.4947	$168.49	$168.50	$168.50
Purchase #2	$11.73	8.329%	$12.707	$12.71	$12.70	$12.70
Purchase #3	$150.38	12.678%	$169.4452	$169.45	$169.45	$169.40
Purchase #4	$105.94	5.672%	$111.9489	$111.95	$111.95	$111.90
Purchase #5	$140.43	6.803%	$149.9835	$149.98	$150.00	$150.00
Purchase #6	$12.29	7.365%	$13.1952	$13.20	$13.20	$13.20
Purchase #7	$148.29	5.770%	$156.8463	$156.85	$156.85	$156.80
7 purchase totals =	$725.53		$782.6208	$782.63	$782.65	$782.50