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	$213.66	4.627%	$223.546	$223.55	$223.55	$223.50
Purchase #2	$249.27	5.296%	$262.4713	$262.47	$262.45	$262.50
Purchase #3	$231.65	4.393%	$241.8264	$241.83	$241.85	$241.80
Purchase #4	$72.93	11.647%	$81.4242	$81.42	$81.40	$81.40
Purchase #5	$6.96	11.697%	$7.7741	$7.77	$7.75	$7.80
Purchase #6	$155.81	9.443%	$170.5231	$170.52	$170.50	$170.50
Purchase #7	$231.51	13.402%	$262.537	$262.54	$262.55	$262.50
7 purchase totals =	$1,161.79		$1,250.1021	$1,250.10	$1,250.05	$1,250.00