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	$122.75	3.847%	$127.4722	$127.47	$127.45	$127.50
Purchase #2	$176.51	3.375%	$182.4672	$182.47	$182.45	$182.50
Purchase #3	$30.49	13.149%	$34.4991	$34.50	$34.50	$34.50
Purchase #4	$172.67	5.626%	$182.3844	$182.38	$182.40	$182.40
Purchase #5	$165.67	4.736%	$173.5161	$173.52	$173.50	$173.50
Purchase #6	$136.59	8.652%	$148.4078	$148.41	$148.40	$148.40
Purchase #7	$211.80	3.503%	$219.2194	$219.22	$219.20	$219.20
7 purchase totals =	$1,016.48		$1,067.9662	$1,067.97	$1,067.90	$1,068.00