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 $119.90   4.673%   $125.5029   $125.50   $125.50   $125.50  
  Purchase #2 $159.40   11.844%   $178.2793   $178.28   $178.30   $178.30  
  Purchase #3 $98.32   4.229%   $102.478   $102.48   $102.50   $102.50  
  Purchase #4 $54.28   6.185%   $57.6372   $57.64   $57.65   $57.60  
  Purchase #5 $234.82   11.218%   $261.1621   $261.16   $261.15   $261.20  
  Purchase #6 $178.98   13.386%   $202.9383   $202.94   $202.95   $202.90  
  Purchase #7 $67.98   6.768%   $72.5809   $72.58   $72.60   $72.60  
  7 purchase totals = $913.68       $1,000.5787   $1,000.58   $1,000.65   $1,000.60