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 $238.95   9.253%   $261.06   $261.06   $261.05   $261.10  
  Purchase #2 $212.54   7.406%   $228.2807   $228.28   $228.30   $228.30  
  Purchase #3 $12.83   5.548%   $13.5418   $13.54   $13.55   $13.50  
  Purchase #4 $125.67   9.458%   $137.5559   $137.56   $137.55   $137.60  
  Purchase #5 $138.84   4.578%   $145.1961   $145.20   $145.20   $145.20  
  Purchase #6 $152.55   6.682%   $162.7434   $162.74   $162.75   $162.70  
  Purchase #7 $142.37   9.250%   $155.5392   $155.54   $155.55   $155.50  
  7 purchase totals = $1,023.75       $1,103.9171   $1,103.92   $1,103.95   $1,103.90