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	$236.83	12.514%	$266.4669	$266.47	$266.45	$266.50
Purchase #2	$126.78	3.793%	$131.5888	$131.59	$131.60	$131.60
Purchase #3	$237.86	4.406%	$248.3401	$248.34	$248.35	$248.30
Purchase #4	$165.67	13.309%	$187.719	$187.72	$187.70	$187.70
Purchase #5	$47.84	8.260%	$51.7916	$51.79	$51.80	$51.80
Purchase #6	$29.87	12.569%	$33.6244	$33.62	$33.60	$33.60
Purchase #7	$129.76	7.790%	$139.8683	$139.87	$139.85	$139.90
7 purchase totals =	$974.61		$1,059.3991	$1,059.40	$1,059.35	$1,059.40