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 $87.89   10.195%   $96.8504   $96.85   $96.85   $96.90  
  Purchase #2 $26.60   11.256%   $29.5941   $29.59   $29.60   $29.60  
  Purchase #3 $218.92   12.685%   $246.69   $246.69   $246.70   $246.70  
  Purchase #4 $62.96   9.661%   $69.0426   $69.04   $69.05   $69.00  
  Purchase #5 $159.95   12.105%   $179.3119   $179.31   $179.30   $179.30  
  Purchase #6 $194.32   8.499%   $210.8353   $210.84   $210.85   $210.80  
  Purchase #7 $56.92   12.265%   $63.9012   $63.90   $63.90   $63.90  
  7 purchase totals = $807.56       $896.2255   $896.22   $896.25   $896.20