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	$205.53	3.759%	$213.2559	$213.26	$213.25	$213.30
Purchase #2	$249.60	12.415%	$280.5878	$280.59	$280.60	$280.60
Purchase #3	$43.50	8.684%	$47.2775	$47.28	$47.30	$47.30
Purchase #4	$179.86	7.229%	$192.8621	$192.86	$192.85	$192.90
Purchase #5	$67.64	3.406%	$69.9438	$69.94	$69.95	$69.90
Purchase #6	$97.75	5.855%	$103.4733	$103.47	$103.45	$103.50
Purchase #7	$238.76	6.815%	$255.0315	$255.03	$255.05	$255.00
7 purchase totals =	$1,082.64		$1,162.4319	$1,162.43	$1,162.45	$1,162.50