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	$143.40	9.461%	$156.9671	$156.97	$156.95	$157.00
Purchase #2	$124.63	13.156%	$141.0263	$141.03	$141.05	$141.00
Purchase #3	$244.49	4.303%	$255.0104	$255.01	$255.00	$255.00
Purchase #4	$50.76	3.179%	$52.3737	$52.37	$52.35	$52.40
Purchase #5	$146.95	12.608%	$165.4775	$165.48	$165.50	$165.50
Purchase #6	$75.45	9.725%	$82.7875	$82.79	$82.80	$82.80
Purchase #7	$104.97	7.337%	$112.6716	$112.67	$112.65	$112.70
7 purchase totals =	$890.65		$966.3141	$966.32	$966.30	$966.40