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	$210.79	7.185%	$225.9353	$225.94	$225.95	$225.90
Purchase #2	$110.37	12.776%	$124.4709	$124.47	$124.45	$124.50
Purchase #3	$52.49	6.716%	$56.0152	$56.02	$56.00	$56.00
Purchase #4	$40.48	4.591%	$42.3384	$42.34	$42.35	$42.30
Purchase #5	$72.89	10.403%	$80.4727	$80.47	$80.45	$80.50
Purchase #6	$86.31	11.298%	$96.0613	$96.06	$96.05	$96.10
Purchase #7	$231.57	11.703%	$258.6706	$258.67	$258.65	$258.70
7 purchase totals =	$804.90		$883.9644	$883.97	$883.90	$884.00