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 $87.51   8.583%   $95.021   $95.02   $95.00   $95.00  
  Purchase #2 $182.49   9.289%   $199.4415   $199.44   $199.45   $199.40  
  Purchase #3 $117.54   4.531%   $122.8657   $122.87   $122.85   $122.90  
  Purchase #4 $250.99   8.155%   $271.4582   $271.46   $271.45   $271.50  
  Purchase #5 $94.35   7.554%   $101.4772   $101.48   $101.50   $101.50  
  Purchase #6 $126.63   7.682%   $136.3577   $136.36   $136.35   $136.40  
  Purchase #7 $158.62   9.655%   $173.9348   $173.93   $173.95   $173.90  
  7 purchase totals = $1,018.13       $1,100.5561   $1,100.56   $1,100.55   $1,100.60