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	$64.66	12.638%	$72.8317	$72.83	$72.85	$72.80
Purchase #2	$151.54	7.188%	$162.4327	$162.43	$162.45	$162.40
Purchase #3	$6.73	10.435%	$7.4323	$7.43	$7.45	$7.40
Purchase #4	$11.36	6.123%	$12.0556	$12.06	$12.05	$12.10
Purchase #5	$235.39	3.191%	$242.9013	$242.90	$242.90	$242.90
Purchase #6	$90.48	5.594%	$95.5415	$95.54	$95.55	$95.50
Purchase #7	$59.98	6.540%	$63.9027	$63.90	$63.90	$63.90
7 purchase totals =	$620.14		$657.0978	$657.09	$657.15	$657.00