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	$184.90	3.283%	$190.9703	$190.97	$190.95	$191.00
Purchase #2	$190.94	3.126%	$196.9088	$196.91	$196.90	$196.90
Purchase #3	$121.37	12.504%	$136.5461	$136.55	$136.55	$136.50
Purchase #4	$91.38	10.116%	$100.624	$100.62	$100.60	$100.60
Purchase #5	$158.93	11.264%	$176.8319	$176.83	$176.85	$176.80
Purchase #6	$241.61	8.623%	$262.444	$262.44	$262.45	$262.40
Purchase #7	$146.32	4.303%	$152.6161	$152.62	$152.60	$152.60
7 purchase totals =	$1,135.45		$1,216.9412	$1,216.94	$1,216.90	$1,216.80