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	$206.69	4.477%	$215.9435	$215.94	$215.95	$215.90
Purchase #2	$185.59	3.337%	$191.7831	$191.78	$191.80	$191.80
Purchase #3	$197.80	7.379%	$212.3957	$212.40	$212.40	$212.40
Purchase #4	$60.53	12.107%	$67.8584	$67.86	$67.85	$67.90
Purchase #5	$42.79	8.734%	$46.5273	$46.53	$46.55	$46.50
Purchase #6	$142.43	4.333%	$148.6015	$148.60	$148.60	$148.60
Purchase #7	$107.97	11.409%	$120.2883	$120.29	$120.30	$120.30
7 purchase totals =	$943.80		$1,003.3978	$1,003.40	$1,003.45	$1,003.40