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	$68.27	13.845%	$77.722	$77.72	$77.70	$77.70
Purchase #2	$106.94	9.293%	$116.8779	$116.88	$116.90	$116.90
Purchase #3	$179.37	4.564%	$187.5564	$187.56	$187.55	$187.60
Purchase #4	$215.70	4.395%	$225.18	$225.18	$225.20	$225.20
Purchase #5	$93.91	11.231%	$104.457	$104.46	$104.45	$104.50
Purchase #6	$190.86	7.638%	$205.4379	$205.44	$205.45	$205.40
Purchase #7	$123.44	13.808%	$140.4846	$140.48	$140.50	$140.50
7 purchase totals =	$978.49		$1,057.7158	$1,057.72	$1,057.75	$1,057.80