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 $91.92   3.408%   $95.0526   $95.05   $95.05   $95.10  
  Purchase #2 $206.81   10.112%   $227.7226   $227.72   $227.70   $227.70  
  Purchase #3 $61.67   8.723%   $67.0495   $67.05   $67.05   $67.00  
  Purchase #4 $11.94   10.118%   $13.1481   $13.15   $13.15   $13.10  
  Purchase #5 $230.76   9.310%   $252.2438   $252.24   $252.25   $252.20  
  Purchase #6 $9.76   8.860%   $10.6247   $10.62   $10.60   $10.60  
  Purchase #7 $92.63   5.874%   $98.0711   $98.07   $98.05   $98.10  
  7 purchase totals = $705.49       $763.9124   $763.90   $763.85   $763.80