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 $56.30   8.734%   $61.2172   $61.22   $61.20   $61.20  
  Purchase #2 $216.71   9.204%   $236.656   $236.66   $236.65   $236.70  
  Purchase #3 $76.88   10.574%   $85.0093   $85.01   $85.00   $85.00  
  Purchase #4 $11.84   4.632%   $12.3884   $12.39   $12.40   $12.40  
  Purchase #5 $238.57   9.688%   $261.6827   $261.68   $261.70   $261.70  
  Purchase #6 $210.44   4.761%   $220.459   $220.46   $220.45   $220.50  
  Purchase #7 $194.65   7.135%   $208.5383   $208.54   $208.55   $208.50  
  7 purchase totals = $1,005.39       $1,085.9509   $1,085.96   $1,085.95   $1,086.00