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 $61.58   9.808%   $67.6198   $67.62   $67.60   $67.60  
  Purchase #2 $231.91   12.631%   $261.2026   $261.20   $261.20   $261.20  
  Purchase #3 $249.56   4.536%   $260.88   $260.88   $260.90   $260.90  
  Purchase #4 $242.58   3.651%   $251.4366   $251.44   $251.45   $251.40  
  Purchase #5 $192.76   13.152%   $218.1118   $218.11   $218.10   $218.10  
  Purchase #6 $185.54   13.413%   $210.4265   $210.43   $210.45   $210.40  
  Purchase #7 $31.96   4.533%   $33.4087   $33.41   $33.40   $33.40  
  7 purchase totals = $1,195.89       $1,303.0860   $1,303.09   $1,303.10   $1,303.00