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 $148.59   6.713%   $158.5648   $158.56   $158.55   $158.60  
  Purchase #2 $230.77   13.684%   $262.3486   $262.35   $262.35   $262.30  
  Purchase #3 $250.70   6.226%   $266.3086   $266.31   $266.30   $266.30  
  Purchase #4 $15.47   10.121%   $17.0357   $17.04   $17.05   $17.00  
  Purchase #5 $79.58   5.601%   $84.0373   $84.04   $84.05   $84.00  
  Purchase #6 $228.42   5.522%   $241.0334   $241.03   $241.05   $241.00  
  Purchase #7 $71.92   4.758%   $75.342   $75.34   $75.35   $75.30  
  7 purchase totals = $1,025.45       $1,104.6704   $1,104.67   $1,104.70   $1,104.50