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 $64.86   5.382%   $68.3508   $68.35   $68.35   $68.40  
  Purchase #2 $246.69   6.438%   $262.5719   $262.57   $262.55   $262.60  
  Purchase #3 $53.72   12.435%   $60.4001   $60.40   $60.40   $60.40  
  Purchase #4 $243.70   3.354%   $251.8737   $251.87   $251.85   $251.90  
  Purchase #5 $199.49   12.579%   $224.5838   $224.58   $224.60   $224.60  
  Purchase #6 $175.53   7.376%   $188.4771   $188.48   $188.50   $188.50  
  Purchase #7 $10.85   7.170%   $11.6279   $11.63   $11.65   $11.60  
  7 purchase totals = $994.84       $1,067.8853   $1,067.88   $1,067.90   $1,068.00