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	$134.35	4.825%	$140.8324	$140.83	$140.85	$140.80
Purchase #2	$233.89	6.223%	$248.445	$248.45	$248.45	$248.40
Purchase #3	$8.90	13.445%	$10.0966	$10.10	$10.10	$10.10
Purchase #4	$79.82	13.550%	$90.6356	$90.64	$90.65	$90.60
Purchase #5	$198.50	13.577%	$225.4503	$225.45	$225.45	$225.50
Purchase #6	$154.99	4.824%	$162.4667	$162.47	$162.45	$162.50
Purchase #7	$76.75	12.737%	$86.5256	$86.53	$86.55	$86.50
7 purchase totals =	$887.20		$964.4522	$964.47	$964.50	$964.40