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	$209.92	10.259%	$231.4557	$231.46	$231.45	$231.50
Purchase #2	$81.36	11.668%	$90.8531	$90.85	$90.85	$90.90
Purchase #3	$143.90	10.867%	$159.5376	$159.54	$159.55	$159.50
Purchase #4	$194.79	3.112%	$200.8519	$200.85	$200.85	$200.90
Purchase #5	$52.42	3.835%	$54.4303	$54.43	$54.45	$54.40
Purchase #6	$80.35	3.116%	$82.8537	$82.85	$82.85	$82.90
Purchase #7	$131.63	9.459%	$144.0809	$144.08	$144.10	$144.10
7 purchase totals =	$894.37		$964.0632	$964.06	$964.10	$964.20