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	$101.93	7.676%	$109.7541	$109.75	$109.75	$109.80
Purchase #2	$136.83	5.521%	$144.3844	$144.38	$144.40	$144.40
Purchase #3	$27.84	12.720%	$31.3812	$31.38	$31.40	$31.40
Purchase #4	$51.51	4.359%	$53.7553	$53.76	$53.75	$53.80
Purchase #5	$234.45	8.199%	$253.6726	$253.67	$253.65	$253.70
Purchase #6	$200.88	7.237%	$215.4177	$215.42	$215.40	$215.40
Purchase #7	$91.68	9.784%	$100.65	$100.65	$100.65	$100.70
7 purchase totals =	$845.12		$909.0153	$909.01	$909.00	$909.20