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	$217.90	9.585%	$238.7857	$238.79	$238.80	$238.80
Purchase #2	$227.90	10.531%	$251.9001	$251.90	$251.90	$251.90
Purchase #3	$119.43	3.620%	$123.7534	$123.75	$123.75	$123.80
Purchase #4	$176.33	3.789%	$183.0111	$183.01	$183.00	$183.00
Purchase #5	$52.33	4.807%	$54.8455	$54.85	$54.85	$54.80
Purchase #6	$108.87	13.463%	$123.5272	$123.53	$123.55	$123.50
Purchase #7	$181.92	3.648%	$188.5564	$188.56	$188.55	$188.60
7 purchase totals =	$1,084.68		$1,164.3794	$1,164.39	$1,164.40	$1,164.40