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	$178.84	11.471%	$199.3547	$199.35	$199.35	$199.40
Purchase #2	$42.40	9.145%	$46.2775	$46.28	$46.30	$46.30
Purchase #3	$198.65	7.477%	$213.5031	$213.50	$213.50	$213.50
Purchase #4	$240.60	9.185%	$262.6991	$262.70	$262.70	$262.70
Purchase #5	$226.59	8.517%	$245.8887	$245.89	$245.90	$245.90
Purchase #6	$179.31	11.679%	$200.2516	$200.25	$200.25	$200.30
Purchase #7	$141.71	11.839%	$158.487	$158.49	$158.50	$158.50
7 purchase totals =	$1,208.10		$1,326.4617	$1,326.46	$1,326.50	$1,326.60