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 $197.69   5.145%   $207.8612   $207.86   $207.85   $207.90  
  Purchase #2 $246.93   4.634%   $258.3727   $258.37   $258.35   $258.40  
  Purchase #3 $174.54   3.438%   $180.5407   $180.54   $180.55   $180.50  
  Purchase #4 $43.99   5.665%   $46.482   $46.48   $46.50   $46.50  
  Purchase #5 $217.47   13.554%   $246.9459   $246.95   $246.95   $246.90  
  Purchase #6 $43.45   13.553%   $49.3388   $49.34   $49.35   $49.30  
  Purchase #7 $199.70   6.263%   $212.2072   $212.21   $212.20   $212.20  
  7 purchase totals = $1,123.77       $1,201.7485   $1,201.75   $1,201.75   $1,201.70