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	$213.66	4.330%	$222.9115	$222.91	$222.90	$222.90
Purchase #2	$86.88	9.817%	$95.409	$95.41	$95.40	$95.40
Purchase #3	$176.36	12.657%	$198.6819	$198.68	$198.70	$198.70
Purchase #4	$163.64	13.284%	$185.3779	$185.38	$185.40	$185.40
Purchase #5	$178.36	5.334%	$187.8737	$187.87	$187.85	$187.90
Purchase #6	$47.38	13.606%	$53.8265	$53.83	$53.85	$53.80
Purchase #7	$51.43	6.178%	$54.6073	$54.61	$54.60	$54.60
7 purchase totals =	$917.71		$998.6878	$998.69	$998.70	$998.70