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	$13.52	10.545%	$14.9457	$14.95	$14.95	$14.90
Purchase #2	$92.27	6.556%	$98.3192	$98.32	$98.30	$98.30
Purchase #3	$63.25	3.520%	$65.4764	$65.48	$65.50	$65.50
Purchase #4	$45.85	3.469%	$47.4405	$47.44	$47.45	$47.40
Purchase #5	$123.37	3.778%	$128.0309	$128.03	$128.05	$128.00
Purchase #6	$136.52	3.332%	$141.0688	$141.07	$141.05	$141.10
Purchase #7	$39.29	10.829%	$43.5447	$43.54	$43.55	$43.50
7 purchase totals =	$514.07		$538.8262	$538.83	$538.85	$538.70