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 $126.86   6.379%   $134.9524   $134.95   $134.95   $135.00  
  Purchase #2 $201.72   7.749%   $217.3513   $217.35   $217.35   $217.40  
  Purchase #3 $167.91   3.361%   $173.5535   $173.55   $173.55   $173.60  
  Purchase #4 $105.55   11.731%   $117.9321   $117.93   $117.95   $117.90  
  Purchase #5 $207.86   4.336%   $216.8728   $216.87   $216.85   $216.90  
  Purchase #6 $220.77   12.844%   $249.1257   $249.13   $249.15   $249.10  
  Purchase #7 $16.95   4.629%   $17.7346   $17.73   $17.75   $17.70  
  7 purchase totals = $1,047.62       $1,127.5224   $1,127.51   $1,127.55   $1,127.60