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	$117.25	5.614%	$123.8324	$123.83	$123.85	$123.80
Purchase #2	$111.75	4.376%	$116.6402	$116.64	$116.65	$116.60
Purchase #3	$182.63	5.395%	$192.4829	$192.48	$192.50	$192.50
Purchase #4	$64.45	4.488%	$67.3425	$67.34	$67.35	$67.30
Purchase #5	$97.65	3.229%	$100.8031	$100.80	$100.80	$100.80
Purchase #6	$120.51	13.758%	$137.0898	$137.09	$137.10	$137.10
Purchase #7	$216.33	10.378%	$238.7807	$238.78	$238.80	$238.80
7 purchase totals =	$910.57		$976.9716	$976.96	$977.05	$976.90