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	$109.72	4.252%	$114.3853	$114.39	$114.40	$114.40
Purchase #2	$182.31	12.585%	$205.2537	$205.25	$205.25	$205.30
Purchase #3	$152.68	10.782%	$169.142	$169.14	$169.15	$169.10
Purchase #4	$10.76	6.477%	$11.4569	$11.46	$11.45	$11.50
Purchase #5	$88.38	12.520%	$99.4452	$99.45	$99.45	$99.40
Purchase #6	$63.81	13.735%	$72.5743	$72.57	$72.55	$72.60
Purchase #7	$225.96	4.676%	$236.5259	$236.53	$236.55	$236.50
7 purchase totals =	$833.62		$908.7833	$908.79	$908.80	$908.80