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	$122.56	3.323%	$126.6327	$126.63	$126.65	$126.60
Purchase #2	$67.39	4.824%	$70.6409	$70.64	$70.65	$70.60
Purchase #3	$124.75	6.212%	$132.4995	$132.50	$132.50	$132.50
Purchase #4	$132.75	5.104%	$139.5256	$139.53	$139.55	$139.50
Purchase #5	$59.94	10.775%	$66.3985	$66.40	$66.40	$66.40
Purchase #6	$127.38	12.172%	$142.8847	$142.88	$142.90	$142.90
Purchase #7	$47.66	12.320%	$53.5317	$53.53	$53.55	$53.50
7 purchase totals =	$682.43		$732.1136	$732.11	$732.20	$732.00