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 $105.38   7.195%   $112.9621   $112.96   $112.95   $113.00  
  Purchase #2 $51.70   8.732%   $56.2144   $56.21   $56.20   $56.20  
  Purchase #3 $201.51   5.475%   $212.5427   $212.54   $212.55   $212.50  
  Purchase #4 $164.44   11.115%   $182.7175   $182.72   $182.70   $182.70  
  Purchase #5 $56.99   8.808%   $62.0097   $62.01   $62.00   $62.00  
  Purchase #6 $237.60   3.714%   $246.4245   $246.42   $246.40   $246.40  
  Purchase #7 $123.63   11.586%   $137.9538   $137.95   $137.95   $138.00  
  7 purchase totals = $941.25       $1,010.8247   $1,010.81   $1,010.75   $1,010.80