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	$72.67	5.529%	$76.6879	$76.69	$76.70	$76.70
Purchase #2	$80.34	3.129%	$82.8538	$82.85	$82.85	$82.90
Purchase #3	$134.40	12.325%	$150.9648	$150.96	$150.95	$151.00
Purchase #4	$94.61	5.672%	$99.9763	$99.98	$100.00	$100.00
Purchase #5	$44.69	8.650%	$48.5557	$48.56	$48.55	$48.60
Purchase #6	$237.56	6.850%	$253.8329	$253.83	$253.85	$253.80
Purchase #7	$46.34	11.731%	$51.7761	$51.78	$51.80	$51.80
7 purchase totals =	$710.61		$764.6475	$764.65	$764.70	$764.80