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	$85.46	8.585%	$92.7967	$92.80	$92.80	$92.80
Purchase #2	$32.96	7.626%	$35.4735	$35.47	$35.45	$35.50
Purchase #3	$219.94	6.220%	$233.6203	$233.62	$233.60	$233.60
Purchase #4	$63.49	13.550%	$72.0929	$72.09	$72.10	$72.10
Purchase #5	$53.86	11.361%	$59.979	$59.98	$60.00	$60.00
Purchase #6	$84.78	3.672%	$87.8931	$87.89	$87.90	$87.90
Purchase #7	$164.81	11.337%	$183.4945	$183.49	$183.50	$183.50
7 purchase totals =	$705.30		$765.3500	$765.34	$765.35	$765.40