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 $57.77   10.697%   $63.9497   $63.95   $63.95   $63.90  
  Purchase #2 $71.56   7.179%   $76.6973   $76.70   $76.70   $76.70  
  Purchase #3 $207.84   6.685%   $221.7341   $221.73   $221.75   $221.70  
  Purchase #4 $172.31   8.672%   $187.2527   $187.25   $187.25   $187.30  
  Purchase #5 $196.69   11.476%   $219.2621   $219.26   $219.25   $219.30  
  Purchase #6 $23.57   7.165%   $25.2588   $25.26   $25.25   $25.30  
  Purchase #7 $196.97   9.854%   $216.3794   $216.38   $216.40   $216.40  
  7 purchase totals = $926.71       $1,010.5341   $1,010.53   $1,010.55   $1,010.60