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	$95.80	7.855%	$103.3251	$103.33	$103.35	$103.30
Purchase #2	$126.51	8.277%	$136.9812	$136.98	$137.00	$137.00
Purchase #3	$165.91	9.310%	$181.3562	$181.36	$181.35	$181.40
Purchase #4	$208.42	13.580%	$236.7234	$236.72	$236.70	$236.70
Purchase #5	$93.71	4.260%	$97.702	$97.70	$97.70	$97.70
Purchase #6	$90.39	11.230%	$100.5408	$100.54	$100.55	$100.50
Purchase #7	$178.86	12.151%	$200.5933	$200.59	$200.60	$200.60
7 purchase totals =	$959.60		$1,057.2220	$1,057.22	$1,057.25	$1,057.20