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	$116.89	13.658%	$132.8548	$132.85	$132.85	$132.90
Purchase #2	$189.33	5.244%	$199.2585	$199.26	$199.25	$199.30
Purchase #3	$38.93	12.732%	$43.8866	$43.89	$43.90	$43.90
Purchase #4	$241.46	8.222%	$261.3128	$261.31	$261.30	$261.30
Purchase #5	$12.76	9.595%	$13.9843	$13.98	$14.00	$14.00
Purchase #6	$164.73	10.651%	$182.2754	$182.28	$182.30	$182.30
Purchase #7	$94.94	3.750%	$98.5003	$98.50	$98.50	$98.50
7 purchase totals =	$859.04		$932.0727	$932.07	$932.10	$932.20