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	$186.31	9.262%	$203.566	$203.57	$203.55	$203.60
Purchase #2	$123.59	9.434%	$135.2495	$135.25	$135.25	$135.20
Purchase #3	$13.55	13.833%	$15.4244	$15.42	$15.40	$15.40
Purchase #4	$179.86	11.410%	$200.382	$200.38	$200.40	$200.40
Purchase #5	$63.59	13.442%	$72.1378	$72.14	$72.15	$72.10
Purchase #6	$54.64	4.111%	$56.8863	$56.89	$56.90	$56.90
Purchase #7	$154.79	3.482%	$160.1798	$160.18	$160.20	$160.20
7 purchase totals =	$776.33		$843.8258	$843.83	$843.85	$843.80