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 $60.77   5.359%   $64.0267   $64.03   $64.05   $64.00  
  Purchase #2 $197.61   10.552%   $218.4618   $218.46   $218.45   $218.50  
  Purchase #3 $149.38   11.231%   $166.1569   $166.16   $166.15   $166.20  
  Purchase #4 $109.72   8.671%   $119.2338   $119.23   $119.25   $119.20  
  Purchase #5 $52.74   6.299%   $56.0621   $56.06   $56.05   $56.10  
  Purchase #6 $242.67   10.727%   $268.7012   $268.70   $268.70   $268.70  
  Purchase #7 $200.80   5.326%   $211.4946   $211.49   $211.50   $211.50  
  7 purchase totals = $1,013.69       $1,104.1371   $1,104.13   $1,104.15   $1,104.20