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 $87.53   6.518%   $93.2352   $93.24   $93.25   $93.20  
  Purchase #2 $127.89   4.168%   $133.2205   $133.22   $133.20   $133.20  
  Purchase #3 $6.95   7.378%   $7.4628   $7.46   $7.45   $7.50  
  Purchase #4 $158.89   3.150%   $163.895   $163.90   $163.90   $163.90  
  Purchase #5 $238.91   9.551%   $261.7283   $261.73   $261.75   $261.70  
  Purchase #6 $157.83   11.227%   $175.5496   $175.55   $175.55   $175.50  
  Purchase #7 $247.29   4.521%   $258.47   $258.47   $258.45   $258.50  
  7 purchase totals = $1,025.29       $1,093.5614   $1,093.57   $1,093.55   $1,093.50