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 $244.91   6.870%   $261.7353   $261.74   $261.75   $261.70  
  Purchase #2 $71.57   6.277%   $76.0624   $76.06   $76.05   $76.10  
  Purchase #3 $204.82   11.765%   $228.9171   $228.92   $228.90   $228.90  
  Purchase #4 $162.98   5.635%   $172.1639   $172.16   $172.15   $172.20  
  Purchase #5 $75.68   10.851%   $83.892   $83.89   $83.90   $83.90  
  Purchase #6 $111.68   5.691%   $118.0357   $118.04   $118.05   $118.00  
  Purchase #7 $153.81   7.699%   $165.6518   $165.65   $165.65   $165.70  
  7 purchase totals = $1,025.45       $1,106.4582   $1,106.46   $1,106.45   $1,106.50