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 $45.34   5.192%   $47.6941   $47.69   $47.70   $47.70  
  Purchase #2 $232.82   11.254%   $259.0216   $259.02   $259.00   $259.00  
  Purchase #3 $111.72   5.832%   $118.2355   $118.24   $118.25   $118.20  
  Purchase #4 $173.28   11.380%   $192.9993   $193.00   $193.00   $193.00  
  Purchase #5 $156.97   12.604%   $176.7545   $176.75   $176.75   $176.80  
  Purchase #6 $27.47   5.362%   $28.9429   $28.94   $28.95   $28.90  
  Purchase #7 $101.38   10.441%   $111.9651   $111.97   $111.95   $112.00  
  7 purchase totals = $848.98       $935.6130   $935.61   $935.60   $935.60