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 $215.86   5.143%   $226.9617   $226.96   $226.95   $227.00  
  Purchase #2 $23.55   5.660%   $24.8829   $24.88   $24.90   $24.90  
  Purchase #3 $49.50   10.297%   $54.597   $54.60   $54.60   $54.60  
  Purchase #4 $43.85   12.484%   $49.3242   $49.32   $49.30   $49.30  
  Purchase #5 $145.81   10.333%   $160.8765   $160.88   $160.90   $160.90  
  Purchase #6 $215.34   5.256%   $226.6583   $226.66   $226.65   $226.70  
  Purchase #7 $11.73   11.177%   $13.0411   $13.04   $13.05   $13.00  
  7 purchase totals = $705.64       $756.3417   $756.34   $756.35   $756.40