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	$201.81	7.856%	$217.6642	$217.66	$217.65	$217.70
Purchase #2	$135.29	13.857%	$154.0371	$154.04	$154.05	$154.00
Purchase #3	$111.37	10.756%	$123.349	$123.35	$123.35	$123.30
Purchase #4	$6.92	8.861%	$7.5332	$7.53	$7.55	$7.50
Purchase #5	$200.49	6.510%	$213.5419	$213.54	$213.55	$213.50
Purchase #6	$6.91	12.276%	$7.7583	$7.76	$7.75	$7.80
Purchase #7	$81.55	11.259%	$90.7317	$90.73	$90.75	$90.70
7 purchase totals =	$744.34		$814.6154	$814.61	$814.65	$814.50