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	$209.83	3.141%	$216.4208	$216.42	$216.40	$216.40
Purchase #2	$87.61	4.165%	$91.259	$91.26	$91.25	$91.30
Purchase #3	$48.77	6.558%	$51.9683	$51.97	$51.95	$52.00
Purchase #4	$129.82	11.382%	$144.5961	$144.60	$144.60	$144.60
Purchase #5	$58.89	13.751%	$66.988	$66.99	$67.00	$67.00
Purchase #6	$191.89	13.326%	$217.4613	$217.46	$217.45	$217.50
Purchase #7	$213.98	6.193%	$227.2318	$227.23	$227.25	$227.20
7 purchase totals =	$940.79		$1,015.9253	$1,015.93	$1,015.90	$1,016.00