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 $84.39   12.274%   $94.748   $94.75   $94.75   $94.70  
  Purchase #2 $214.80   10.547%   $237.455   $237.46   $237.45   $237.50  
  Purchase #3 $245.26   6.429%   $261.0278   $261.03   $261.05   $261.00  
  Purchase #4 $82.87   9.444%   $90.6962   $90.70   $90.70   $90.70  
  Purchase #5 $18.54   12.194%   $20.8008   $20.80   $20.80   $20.80  
  Purchase #6 $76.57   9.604%   $83.9238   $83.92   $83.90   $83.90  
  Purchase #7 $204.55   10.301%   $225.6207   $225.62   $225.60   $225.60  
  7 purchase totals = $926.98       $1,014.2723   $1,014.28   $1,014.25   $1,014.20