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	$65.50	3.272%	$67.6432	$67.64	$67.65	$67.60
Purchase #2	$56.49	5.334%	$59.5032	$59.50	$59.50	$59.50
Purchase #3	$164.72	9.481%	$180.3371	$180.34	$180.35	$180.30
Purchase #4	$31.63	12.772%	$35.6698	$35.67	$35.65	$35.70
Purchase #5	$12.38	3.755%	$12.8449	$12.84	$12.85	$12.80
Purchase #6	$137.45	11.168%	$152.8004	$152.80	$152.80	$152.80
Purchase #7	$58.63	8.541%	$63.6376	$63.64	$63.65	$63.60
7 purchase totals =	$526.80		$572.4362	$572.43	$572.45	$572.30