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 $44.95   7.824%   $48.4669   $48.47   $48.45   $48.50  
  Purchase #2 $67.91   5.471%   $71.6254   $71.63   $71.65   $71.60  
  Purchase #3 $227.37   6.450%   $242.0354   $242.04   $242.05   $242.00  
  Purchase #4 $246.87   5.608%   $260.7145   $260.71   $260.70   $260.70  
  Purchase #5 $146.60   3.314%   $151.4583   $151.46   $151.45   $151.50  
  Purchase #6 $77.48   4.829%   $81.2215   $81.22   $81.20   $81.20  
  Purchase #7 $138.39   12.591%   $155.8147   $155.81   $155.80   $155.80  
  7 purchase totals = $949.57       $1,011.3367   $1,011.34   $1,011.30   $1,011.30