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	$124.95	11.626%	$139.4767	$139.48	$139.50	$139.50
Purchase #2	$164.39	3.215%	$169.6751	$169.68	$169.70	$169.70
Purchase #3	$106.55	5.530%	$112.4422	$112.44	$112.45	$112.40
Purchase #4	$215.45	4.685%	$225.5438	$225.54	$225.55	$225.50
Purchase #5	$228.59	5.807%	$241.8642	$241.86	$241.85	$241.90
Purchase #6	$28.39	5.127%	$29.8456	$29.85	$29.85	$29.80
Purchase #7	$123.35	5.336%	$129.932	$129.93	$129.95	$129.90
7 purchase totals =	$991.67		$1,048.7796	$1,048.78	$1,048.85	$1,048.70