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	$150.56	10.597%	$166.5148	$166.51	$166.50	$166.50
Purchase #2	$104.94	10.612%	$116.0762	$116.08	$116.10	$116.10
Purchase #3	$19.43	11.755%	$21.714	$21.71	$21.70	$21.70
Purchase #4	$109.77	9.742%	$120.4638	$120.46	$120.45	$120.50
Purchase #5	$129.98	3.285%	$134.2498	$134.25	$134.25	$134.20
Purchase #6	$187.79	4.754%	$196.7175	$196.72	$196.70	$196.70
Purchase #7	$45.88	3.136%	$47.3188	$47.32	$47.30	$47.30
7 purchase totals =	$748.35		$803.0549	$803.05	$803.00	$803.00