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	$126.63	10.288%	$139.6577	$139.66	$139.65	$139.70
Purchase #2	$143.52	12.542%	$161.5203	$161.52	$161.50	$161.50
Purchase #3	$179.66	9.615%	$196.9343	$196.93	$196.95	$196.90
Purchase #4	$62.68	4.523%	$65.515	$65.52	$65.50	$65.50
Purchase #5	$224.40	3.687%	$232.6736	$232.67	$232.65	$232.70
Purchase #6	$79.87	7.577%	$85.9217	$85.92	$85.90	$85.90
Purchase #7	$200.87	7.205%	$215.3427	$215.34	$215.35	$215.30
7 purchase totals =	$1,017.63		$1,097.5653	$1,097.56	$1,097.50	$1,097.50