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 $41.73   13.376%   $47.3118   $47.31   $47.30   $47.30  
  Purchase #2 $151.27   7.681%   $162.889   $162.89   $162.90   $162.90  
  Purchase #3 $78.78   8.670%   $85.6102   $85.61   $85.60   $85.60  
  Purchase #4 $188.44   10.314%   $207.8757   $207.88   $207.90   $207.90  
  Purchase #5 $235.45   3.639%   $244.018   $244.02   $244.00   $244.00  
  Purchase #6 $145.30   7.830%   $156.677   $156.68   $156.70   $156.70  
  Purchase #7 $186.85   13.826%   $212.6839   $212.68   $212.70   $212.70  
  7 purchase totals = $1,027.82       $1,117.0656   $1,117.07   $1,117.10   $1,117.10