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	$104.46	3.226%	$107.8299	$107.83	$107.85	$107.80
Purchase #2	$29.92	4.669%	$31.317	$31.32	$31.30	$31.30
Purchase #3	$59.61	4.295%	$62.1702	$62.17	$62.15	$62.20
Purchase #4	$209.34	4.182%	$218.0946	$218.09	$218.10	$218.10
Purchase #5	$217.82	12.312%	$244.638	$244.64	$244.65	$244.60
Purchase #6	$154.40	11.718%	$172.4926	$172.49	$172.50	$172.50
Purchase #7	$6.39	9.767%	$7.0141	$7.01	$7.00	$7.00
7 purchase totals =	$781.94		$843.5564	$843.55	$843.55	$843.50