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	$213.97	6.501%	$227.8802	$227.88	$227.90	$227.90
Purchase #2	$66.81	3.783%	$69.3374	$69.34	$69.35	$69.30
Purchase #3	$88.34	10.631%	$97.7314	$97.73	$97.75	$97.70
Purchase #4	$75.64	3.647%	$78.3986	$78.40	$78.40	$78.40
Purchase #5	$124.70	12.527%	$140.3212	$140.32	$140.30	$140.30
Purchase #6	$89.59	12.248%	$100.563	$100.56	$100.55	$100.60
Purchase #7	$128.81	4.665%	$134.819	$134.82	$134.80	$134.80
7 purchase totals =	$787.86		$849.0508	$849.05	$849.05	$849.00