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	$103.25	5.142%	$108.5591	$108.56	$108.55	$108.60
Purchase #2	$116.59	8.874%	$126.9362	$126.94	$126.95	$126.90
Purchase #3	$46.45	8.820%	$50.5469	$50.55	$50.55	$50.50
Purchase #4	$188.44	5.209%	$198.2558	$198.26	$198.25	$198.30
Purchase #5	$243.27	9.152%	$265.5341	$265.53	$265.55	$265.50
Purchase #6	$173.36	13.172%	$196.195	$196.20	$196.20	$196.20
Purchase #7	$94.52	6.351%	$100.523	$100.52	$100.50	$100.50
7 purchase totals =	$965.88		$1,046.5501	$1,046.56	$1,046.55	$1,046.50