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	$62.57	13.607%	$71.0839	$71.08	$71.10	$71.10
Purchase #2	$225.33	13.595%	$255.9636	$255.96	$255.95	$256.00
Purchase #3	$63.91	8.559%	$69.3801	$69.38	$69.40	$69.40
Purchase #4	$228.46	4.866%	$239.5769	$239.58	$239.60	$239.60
Purchase #5	$121.85	4.864%	$127.7768	$127.78	$127.80	$127.80
Purchase #6	$19.95	4.710%	$20.8896	$20.89	$20.90	$20.90
Purchase #7	$113.52	12.631%	$127.8587	$127.86	$127.85	$127.90
7 purchase totals =	$835.59		$912.5296	$912.53	$912.60	$912.70