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	$127.65	7.683%	$137.4573	$137.46	$137.45	$137.50
Purchase #2	$239.56	9.320%	$261.887	$261.89	$261.90	$261.90
Purchase #3	$30.32	10.718%	$33.5697	$33.57	$33.55	$33.60
Purchase #4	$121.89	12.475%	$137.0958	$137.10	$137.10	$137.10
Purchase #5	$246.79	10.200%	$271.9626	$271.96	$271.95	$272.00
Purchase #6	$201.55	8.727%	$219.1393	$219.14	$219.15	$219.10
Purchase #7	$36.40	12.238%	$40.8546	$40.85	$40.85	$40.90
7 purchase totals =	$1,004.16		$1,101.9663	$1,101.97	$1,101.95	$1,102.10