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	$37.68	5.625%	$39.7995	$39.80	$39.80	$39.80
Purchase #2	$73.97	5.788%	$78.2514	$78.25	$78.25	$78.30
Purchase #3	$130.26	9.650%	$142.8301	$142.83	$142.85	$142.80
Purchase #4	$215.94	12.343%	$242.5935	$242.59	$242.60	$242.60
Purchase #5	$172.65	5.304%	$181.8074	$181.81	$181.80	$181.80
Purchase #6	$237.74	3.203%	$245.3548	$245.35	$245.35	$245.40
Purchase #7	$114.66	7.646%	$123.4269	$123.43	$123.45	$123.40
7 purchase totals =	$982.90		$1,054.0636	$1,054.06	$1,054.10	$1,054.10