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 $201.50   5.637%   $212.8586   $212.86   $212.85   $212.90  
  Purchase #2 $232.38   8.114%   $251.2353   $251.24   $251.25   $251.20  
  Purchase #3 $24.94   6.794%   $26.6344   $26.63   $26.65   $26.60  
  Purchase #4 $46.61   3.493%   $48.2381   $48.24   $48.25   $48.20  
  Purchase #5 $231.42   13.425%   $262.4881   $262.49   $262.50   $262.50  
  Purchase #6 $201.53   5.343%   $212.2977   $212.30   $212.30   $212.30  
  Purchase #7 $172.35   10.746%   $190.8707   $190.87   $190.85   $190.90  
  7 purchase totals = $1,110.73       $1,204.6229   $1,204.63   $1,204.65   $1,204.60