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 $94.76   8.563%   $102.8743   $102.87   $102.85   $102.90  
  Purchase #2 $85.30   5.180%   $89.7185   $89.72   $89.70   $89.70  
  Purchase #3 $111.61   6.837%   $119.2408   $119.24   $119.25   $119.20  
  Purchase #4 $222.98   5.615%   $235.5003   $235.50   $235.50   $235.50  
  Purchase #5 $147.99   6.713%   $157.9246   $157.92   $157.90   $157.90  
  Purchase #6 $241.49   8.230%   $261.3646   $261.36   $261.35   $261.40  
  Purchase #7 $134.40   7.187%   $144.0593   $144.06   $144.05   $144.10  
  7 purchase totals = $1,038.53       $1,110.6824   $1,110.67   $1,110.60   $1,110.70