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 $87.59   7.153%   $93.8553   $93.86   $93.85   $93.90  
  Purchase #2 $173.45   13.349%   $196.6038   $196.60   $196.60   $196.60  
  Purchase #3 $66.28   4.667%   $69.3733   $69.37   $69.35   $69.40  
  Purchase #4 $244.46   5.766%   $258.5556   $258.56   $258.55   $258.60  
  Purchase #5 $237.49   7.849%   $256.1306   $256.13   $256.15   $256.10  
  Purchase #6 $230.97   13.394%   $261.9061   $261.91   $261.90   $261.90  
  Purchase #7 $119.47   3.486%   $123.6347   $123.63   $123.65   $123.60  
  7 purchase totals = $1,159.71       $1,260.0594   $1,260.06   $1,260.05   $1,260.10