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 $57.81   7.698%   $62.2602   $62.26   $62.25   $62.30  
  Purchase #2 $209.65   10.686%   $232.0532   $232.05   $232.05   $232.10  
  Purchase #3 $215.86   4.236%   $225.0038   $225.00   $225.00   $225.00  
  Purchase #4 $165.74   12.487%   $186.436   $186.44   $186.45   $186.40  
  Purchase #5 $193.87   5.582%   $204.6918   $204.69   $204.70   $204.70  
  Purchase #6 $77.97   12.434%   $87.6648   $87.66   $87.65   $87.70  
  Purchase #7 $102.41   12.827%   $115.5461   $115.55   $115.55   $115.50  
  7 purchase totals = $1,023.31       $1,113.6559   $1,113.65   $1,113.65   $1,113.70