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 $115.92   8.359%   $125.6098   $125.61   $125.60   $125.60  
  Purchase #2 $46.58   7.285%   $49.9734   $49.97   $49.95   $50.00  
  Purchase #3 $22.44   8.334%   $24.3101   $24.31   $24.30   $24.30  
  Purchase #4 $216.43   5.668%   $228.6973   $228.70   $228.70   $228.70  
  Purchase #5 $248.50   8.732%   $270.199   $270.20   $270.20   $270.20  
  Purchase #6 $95.25   7.444%   $102.3404   $102.34   $102.35   $102.30  
  Purchase #7 $134.59   11.399%   $149.9319   $149.93   $149.95   $149.90  
  7 purchase totals = $879.71       $951.0619   $951.06   $951.05   $951.00