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	$220.77	4.147%	$229.9253	$229.93	$229.95	$229.90
Purchase #2	$117.85	8.473%	$127.8354	$127.84	$127.85	$127.80
Purchase #3	$196.53	11.635%	$219.3963	$219.40	$219.40	$219.40
Purchase #4	$156.70	7.549%	$168.5293	$168.53	$168.55	$168.50
Purchase #5	$40.97	3.680%	$42.4777	$42.48	$42.50	$42.50
Purchase #6	$214.60	7.857%	$231.4611	$231.46	$231.45	$231.50
Purchase #7	$14.32	10.456%	$15.8173	$15.82	$15.80	$15.80
7 purchase totals =	$961.74		$1,035.4424	$1,035.46	$1,035.50	$1,035.40