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	$149.81	4.698%	$156.8481	$156.85	$156.85	$156.80
Purchase #2	$66.32	7.431%	$71.2482	$71.25	$71.25	$71.20
Purchase #3	$178.78	7.337%	$191.8971	$191.90	$191.90	$191.90
Purchase #4	$60.60	8.312%	$65.6371	$65.64	$65.65	$65.60
Purchase #5	$142.83	5.450%	$150.6142	$150.61	$150.60	$150.60
Purchase #6	$13.70	9.862%	$15.0511	$15.05	$15.05	$15.10
Purchase #7	$227.84	6.127%	$241.7998	$241.80	$241.80	$241.80
7 purchase totals =	$839.88		$893.0956	$893.10	$893.10	$893.00