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 $92.90   3.488%   $96.1404   $96.14   $96.15   $96.10  
  Purchase #2 $184.97   10.832%   $205.006   $205.01   $205.00   $205.00  
  Purchase #3 $38.92   8.338%   $42.1651   $42.17   $42.15   $42.20  
  Purchase #4 $49.28   7.714%   $53.0815   $53.08   $53.10   $53.10  
  Purchase #5 $180.59   11.327%   $201.0454   $201.05   $201.05   $201.00  
  Purchase #6 $197.64   9.609%   $216.6312   $216.63   $216.65   $216.60  
  Purchase #7 $121.38   13.653%   $137.952   $137.95   $137.95   $138.00  
  7 purchase totals = $865.68       $952.0216   $952.03   $952.05   $952.00