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 $58.38   9.687%   $64.0353   $64.04   $64.05   $64.00  
  Purchase #2 $189.61   3.412%   $196.0795   $196.08   $196.10   $196.10  
  Purchase #3 $66.62   13.583%   $75.669   $75.67   $75.65   $75.70  
  Purchase #4 $230.36   4.681%   $241.1432   $241.14   $241.15   $241.10  
  Purchase #5 $112.78   11.381%   $125.6155   $125.62   $125.60   $125.60  
  Purchase #6 $190.91   4.680%   $199.8446   $199.84   $199.85   $199.80  
  Purchase #7 $104.31   7.725%   $112.3679   $112.37   $112.35   $112.40  
  7 purchase totals = $952.97       $1,014.7550   $1,014.76   $1,014.75   $1,014.70