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	$108.42	4.534%	$113.3358	$113.34	$113.35	$113.30
Purchase #2	$102.25	12.345%	$114.8728	$114.87	$114.85	$114.90
Purchase #3	$69.32	13.102%	$78.4023	$78.40	$78.40	$78.40
Purchase #4	$54.66	6.612%	$58.2741	$58.27	$58.25	$58.30
Purchase #5	$213.86	5.636%	$225.9131	$225.91	$225.90	$225.90
Purchase #6	$128.90	12.120%	$144.5227	$144.52	$144.50	$144.50
Purchase #7	$146.74	11.738%	$163.9643	$163.96	$163.95	$164.00
7 purchase totals =	$824.15		$899.2851	$899.27	$899.20	$899.30