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 $192.68   9.542%   $211.0655   $211.07   $211.05   $211.10  
  Purchase #2 $175.45   12.539%   $197.4497   $197.45   $197.45   $197.40  
  Purchase #3 $177.95   7.229%   $190.814   $190.81   $190.80   $190.80  
  Purchase #4 $124.67   7.193%   $133.6375   $133.64   $133.65   $133.60  
  Purchase #5 $173.33   4.570%   $181.2512   $181.25   $181.25   $181.30  
  Purchase #6 $23.34   13.870%   $26.5773   $26.58   $26.60   $26.60  
  Purchase #7 $155.77   4.718%   $163.1192   $163.12   $163.10   $163.10  
  7 purchase totals = $1,023.19       $1,103.9144   $1,103.92   $1,103.90   $1,103.90