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	$228.55	13.453%	$259.2968	$259.30	$259.30	$259.30
Purchase #2	$221.68	12.346%	$249.0486	$249.05	$249.05	$249.00
Purchase #3	$47.55	10.338%	$52.4657	$52.47	$52.45	$52.50
Purchase #4	$34.32	9.239%	$37.4908	$37.49	$37.50	$37.50
Purchase #5	$141.32	12.816%	$159.4316	$159.43	$159.45	$159.40
Purchase #6	$18.77	10.292%	$20.7018	$20.70	$20.70	$20.70
Purchase #7	$143.71	6.166%	$152.5712	$152.57	$152.55	$152.60
7 purchase totals =	$835.90		$931.0065	$931.01	$931.00	$931.00