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	$31.65	8.581%	$34.3659	$34.37	$34.35	$34.40
Purchase #2	$189.92	5.288%	$199.963	$199.96	$199.95	$200.00
Purchase #3	$239.78	8.408%	$259.9407	$259.94	$259.95	$259.90
Purchase #4	$145.95	3.848%	$151.5662	$151.57	$151.55	$151.60
Purchase #5	$111.66	10.512%	$123.3977	$123.40	$123.40	$123.40
Purchase #6	$95.44	8.410%	$103.4665	$103.47	$103.45	$103.50
Purchase #7	$168.51	7.278%	$180.7742	$180.77	$180.75	$180.80
7 purchase totals =	$982.91		$1,053.4742	$1,053.48	$1,053.40	$1,053.60