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	$107.83	6.152%	$114.4637	$114.46	$114.45	$114.50
Purchase #2	$79.70	3.703%	$82.6513	$82.65	$82.65	$82.70
Purchase #3	$199.25	13.143%	$225.4374	$225.44	$225.45	$225.40
Purchase #4	$170.31	4.788%	$178.4644	$178.46	$178.45	$178.50
Purchase #5	$166.87	12.384%	$187.5352	$187.54	$187.55	$187.50
Purchase #6	$116.94	7.506%	$125.7175	$125.72	$125.70	$125.70
Purchase #7	$175.48	8.738%	$190.8134	$190.81	$190.80	$190.80
7 purchase totals =	$1,016.38		$1,105.0829	$1,105.08	$1,105.05	$1,105.10