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 $168.83   8.813%   $183.709   $183.71   $183.70   $183.70  
  Purchase #2 $222.73   9.784%   $244.5219   $244.52   $244.50   $244.50  
  Purchase #3 $23.85   8.208%   $25.8076   $25.81   $25.80   $25.80  
  Purchase #4 $219.32   8.833%   $238.6925   $238.69   $238.70   $238.70  
  Purchase #5 $74.91   5.170%   $78.7828   $78.78   $78.80   $78.80  
  Purchase #6 $232.31   12.752%   $261.9342   $261.93   $261.95   $261.90  
  Purchase #7 $26.84   6.538%   $28.5948   $28.59   $28.60   $28.60  
  7 purchase totals = $968.79       $1,062.0428   $1,062.03   $1,062.05   $1,062.00