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 $146.48   7.508%   $157.4777   $157.48   $157.50   $157.50  
  Purchase #2 $101.92   8.590%   $110.6749   $110.67   $110.65   $110.70  
  Purchase #3 $206.46   5.826%   $218.4884   $218.49   $218.50   $218.50  
  Purchase #4 $178.40   6.853%   $190.6258   $190.63   $190.65   $190.60  
  Purchase #5 $241.47   6.826%   $257.9527   $257.95   $257.95   $258.00  
  Purchase #6 $168.54   8.833%   $183.4271   $183.43   $183.45   $183.40  
  Purchase #7 $104.66   12.525%   $117.7687   $117.77   $117.75   $117.80  
  7 purchase totals = $1,147.93       $1,236.4153   $1,236.42   $1,236.45   $1,236.50