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	$49.89	10.423%	$55.09	$55.09	$55.10	$55.10
Purchase #2	$132.63	10.396%	$146.4182	$146.42	$146.40	$146.40
Purchase #3	$126.46	4.293%	$131.8889	$131.89	$131.90	$131.90
Purchase #4	$73.78	3.106%	$76.0716	$76.07	$76.05	$76.10
Purchase #5	$95.89	5.282%	$100.9549	$100.95	$100.95	$101.00
Purchase #6	$37.40	4.575%	$39.1111	$39.11	$39.10	$39.10
Purchase #7	$191.58	12.647%	$215.8091	$215.81	$215.80	$215.80
7 purchase totals =	$707.63		$765.3438	$765.34	$765.30	$765.40