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	$136.37	4.699%	$142.778	$142.78	$142.80	$142.80
Purchase #2	$213.99	10.846%	$237.1994	$237.20	$237.20	$237.20
Purchase #3	$39.42	10.284%	$43.474	$43.47	$43.45	$43.50
Purchase #4	$88.67	12.474%	$99.7307	$99.73	$99.75	$99.70
Purchase #5	$104.59	7.580%	$112.5179	$112.52	$112.50	$112.50
Purchase #6	$148.42	3.151%	$153.0967	$153.10	$153.10	$153.10
Purchase #7	$236.25	9.629%	$258.9985	$259.00	$259.00	$259.00
7 purchase totals =	$967.71		$1,047.7952	$1,047.80	$1,047.80	$1,047.80