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	$42.96	8.145%	$46.4591	$46.46	$46.45	$46.50
Purchase #2	$196.37	3.593%	$203.4256	$203.43	$203.45	$203.40
Purchase #3	$128.53	8.774%	$139.8072	$139.81	$139.80	$139.80
Purchase #4	$98.72	4.829%	$103.4872	$103.49	$103.50	$103.50
Purchase #5	$107.89	9.274%	$117.8957	$117.90	$117.90	$117.90
Purchase #6	$223.27	7.425%	$239.8478	$239.85	$239.85	$239.80
Purchase #7	$44.68	4.333%	$46.616	$46.62	$46.60	$46.60
7 purchase totals =	$842.42		$897.5386	$897.56	$897.55	$897.50