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	$92.27	3.604%	$95.5954	$95.60	$95.60	$95.60
Purchase #2	$52.80	11.796%	$59.0283	$59.03	$59.05	$59.00
Purchase #3	$242.68	5.688%	$256.4836	$256.48	$256.50	$256.50
Purchase #4	$150.90	12.618%	$169.9406	$169.94	$169.95	$169.90
Purchase #5	$161.29	11.831%	$180.3722	$180.37	$180.35	$180.40
Purchase #6	$31.60	12.690%	$35.61	$35.61	$35.60	$35.60
Purchase #7	$63.55	9.533%	$69.6082	$69.61	$69.60	$69.60
7 purchase totals =	$795.09		$866.6383	$866.64	$866.65	$866.60