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	$239.50	8.229%	$259.2085	$259.21	$259.20	$259.20
Purchase #2	$23.94	8.154%	$25.8921	$25.89	$25.90	$25.90
Purchase #3	$180.49	10.497%	$199.436	$199.44	$199.45	$199.40
Purchase #4	$67.59	4.392%	$70.5586	$70.56	$70.55	$70.60
Purchase #5	$155.39	5.752%	$164.328	$164.33	$164.35	$164.30
Purchase #6	$7.88	12.513%	$8.866	$8.87	$8.85	$8.90
Purchase #7	$105.67	10.336%	$116.5921	$116.59	$116.60	$116.60
7 purchase totals =	$780.46		$844.8813	$844.89	$844.90	$844.90