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 $183.86   7.612%   $197.8554   $197.86   $197.85   $197.90  
  Purchase #2 $95.54   6.342%   $101.5991   $101.60   $101.60   $101.60  
  Purchase #3 $42.72   7.678%   $46   $46.00   $46.00   $46.00  
  Purchase #4 $226.40   8.280%   $245.1459   $245.15   $245.15   $245.10  
  Purchase #5 $54.39   11.327%   $60.5508   $60.55   $60.55   $60.60  
  Purchase #6 $156.76   11.619%   $174.9739   $174.97   $174.95   $175.00  
  Purchase #7 $95.92   7.433%   $103.0497   $103.05   $103.05   $103.00  
  7 purchase totals = $855.59       $929.1748   $929.18   $929.15   $929.20