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	$250.32	12.587%	$281.8278	$281.83	$281.85	$281.80
Purchase #2	$157.58	4.210%	$164.2141	$164.21	$164.20	$164.20
Purchase #3	$44.57	6.175%	$47.3222	$47.32	$47.30	$47.30
Purchase #4	$35.59	5.308%	$37.4791	$37.48	$37.50	$37.50
Purchase #5	$189.94	12.439%	$213.5666	$213.57	$213.55	$213.60
Purchase #6	$166.30	4.392%	$173.6039	$173.60	$173.60	$173.60
Purchase #7	$139.37	12.320%	$156.5404	$156.54	$156.55	$156.50
7 purchase totals =	$983.67		$1,074.5541	$1,074.55	$1,074.55	$1,074.50