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	$225.40	5.799%	$238.4709	$238.47	$238.45	$238.50
Purchase #2	$134.29	7.549%	$144.4276	$144.43	$144.45	$144.40
Purchase #3	$44.48	6.780%	$47.4957	$47.50	$47.50	$47.50
Purchase #4	$48.38	3.108%	$49.8837	$49.88	$49.90	$49.90
Purchase #5	$158.42	10.506%	$175.0636	$175.06	$175.05	$175.10
Purchase #6	$222.97	5.321%	$234.8342	$234.83	$234.85	$234.80
Purchase #7	$119.97	13.572%	$136.2523	$136.25	$136.25	$136.30
7 purchase totals =	$953.91		$1,026.4280	$1,026.42	$1,026.45	$1,026.50