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	$46.26	11.225%	$51.4527	$51.45	$51.45	$51.50
Purchase #2	$70.37	4.150%	$73.2904	$73.29	$73.30	$73.30
Purchase #3	$109.83	10.111%	$120.9349	$120.93	$120.95	$120.90
Purchase #4	$132.44	7.405%	$142.2472	$142.25	$142.25	$142.20
Purchase #5	$235.54	9.266%	$257.3651	$257.37	$257.35	$257.40
Purchase #6	$10.39	4.725%	$10.8809	$10.88	$10.90	$10.90
Purchase #7	$247.69	11.789%	$276.8902	$276.89	$276.90	$276.90
7 purchase totals =	$852.52		$933.0614	$933.06	$933.10	$933.10