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 $67.57   13.377%   $76.6088   $76.61   $76.60   $76.60  
  Purchase #2 $189.27   10.764%   $209.643   $209.64   $209.65   $209.60  
  Purchase #3 $52.61   5.854%   $55.6898   $55.69   $55.70   $55.70  
  Purchase #4 $107.55   10.364%   $118.6965   $118.70   $118.70   $118.70  
  Purchase #5 $22.53   7.749%   $24.2758   $24.28   $24.30   $24.30  
  Purchase #6 $175.57   8.766%   $190.9605   $190.96   $190.95   $191.00  
  Purchase #7 $190.87   8.280%   $206.674   $206.67   $206.65   $206.70  
  7 purchase totals = $805.97       $882.5484   $882.55   $882.55   $882.60