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 $119.67   5.230%   $125.9287   $125.93   $125.95   $125.90  
  Purchase #2 $31.59   12.445%   $35.5214   $35.52   $35.50   $35.50  
  Purchase #3 $200.56   8.180%   $216.9658   $216.97   $216.95   $217.00  
  Purchase #4 $107.71   6.342%   $114.541   $114.54   $114.55   $114.50  
  Purchase #5 $50.61   5.440%   $53.3632   $53.36   $53.35   $53.40  
  Purchase #6 $147.38   8.380%   $159.7304   $159.73   $159.75   $159.70  
  Purchase #7 $24.50   7.532%   $26.3453   $26.35   $26.35   $26.30  
  7 purchase totals = $682.02       $732.3958   $732.40   $732.40   $732.30