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	$123.54	6.492%	$131.5602	$131.56	$131.55	$131.60
Purchase #2	$117.35	4.657%	$122.815	$122.82	$122.80	$122.80
Purchase #3	$90.96	7.783%	$98.0394	$98.04	$98.05	$98.00
Purchase #4	$178.40	4.136%	$185.7786	$185.78	$185.80	$185.80
Purchase #5	$250.39	8.447%	$271.5404	$271.54	$271.55	$271.50
Purchase #6	$123.89	12.699%	$139.6228	$139.62	$139.60	$139.60
Purchase #7	$196.76	10.538%	$217.4946	$217.49	$217.50	$217.50
7 purchase totals =	$1,081.29		$1,166.8510	$1,166.85	$1,166.85	$1,166.80