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 $164.90   6.126%   $175.0018   $175.00   $175.00   $175.00  
  Purchase #2 $201.74   8.405%   $218.6962   $218.70   $218.70   $218.70  
  Purchase #3 $187.59   5.551%   $198.0031   $198.00   $198.00   $198.00  
  Purchase #4 $218.54   5.221%   $229.95   $229.95   $229.95   $230.00  
  Purchase #5 $232.46   7.615%   $250.1618   $250.16   $250.15   $250.20  
  Purchase #6 $190.69   6.682%   $203.4319   $203.43   $203.45   $203.40  
  Purchase #7 $215.72   6.692%   $230.156   $230.16   $230.15   $230.20  
  7 purchase totals = $1,411.64       $1,505.4008   $1,505.40   $1,505.40   $1,505.50